GB2317718A

GB2317718A - Reference current circuit and reference voltage circuit

Info

Publication number: GB2317718A
Application number: GB9725549A
Authority: GB
Inventors: Katsuiji Kimura
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1993-12-08
Filing date: 1994-12-07
Publication date: 1998-04-01
Anticipated expiration: 2014-12-07
Also published as: GB9725550D0; GB9725549D0; GB2317719A; GB2317718B; GB2317719B

Abstract

A reference current circuit (figure 8) or reference voltage circuit prevents the occurrence of the difference collector current associated with the Early Voltage Effect. The circuit comprises transistors Q1, Q2, Q5, Q6 with the emitter area of Q2 being 'e' times that of Q1, Q5 and Q6, where 'e' is the base of natural logarithms, the overall effect of this being that the collector currents of Q1 and Q2 are equal to each other. A similar result may be obtained by using MOS transistors (figures 17 and 18) where the transconductance of one transistor (M2, figures 17 and 18) is four times as large as the transconductance of the others. There is a resistor R1 between the collector and base of Q1. Additionally the circuit includes transistors Q7 and Q8, and a resistor R5 connected between the base of Q1 and the collector Q6. In the voltage circuit, an output terminal T3 is connected to the node between resistor R5 and the collector Q6.

Description

REFERENCE CURRENT CIRCUIT AND REFERENCE VOLTAGE CIRCUIT Background of the Invention: This invention relates to a reference current circuit and a reference voltage circuit.

A known reference current circuit is disclosed in IEEE Journal of Solid-State Circuits, Vol.

SC-22, No. 6, pp. 1139-1143, Dec. 1987.

In the manner which will later be described more in detail, the known reference current circuit comprises a primary pair of first and second transistors and a secondary pair of third and fourth transistors.

The first transistor has a first emitter electrode connected to ground through a resistor. The second transistor has a second emitter electrode grounded and a second base electrode connected to a first base electrode of the first transistor. The third transistor has a third emitter electrode connected to a power supply terminal which is supplied with a power supply voltage from a power supply unit. The third transistor has a third collector electrode connected to a first collector electrode of the first transistor. The fourth transistor has a fourth emitter electrode connected to the power supply terminal and a fourth base electrode connected to a third base electrode of the third transistor. The fourth transistor has a fourth collector electrode connected to the fourth base electrode of the fourth transistor and a second collector electrode or the second transistor.

A fifth transistor has a fifth emitter electrode connected to the power supply terminal and a fifth base electrode connected to the third collector electrode of the third transistor. A sixth transistor has a sixth emitter electrode grounded and a sixth collector electrode connected to a fifth collector electrode of the fifth transistor. The sixth transistor has a sixth base electrode connected to the sixth collector electrode of the sixth transistor and the first base electrode of the first transistor.

The first transistor has an emitter area which is K1 times as large as a unit emitter area of a unit transistor. Each of the second through the fourth transistors has an emitter area which is equal to the unit emitter area. Each of the fifth and the sixth transistors has an emitter area which is two times as large as the unit emitter area. Inasmuch as the fifth transistor has the emitter area which is two times as large as the unit emitter area of the unit transistor, a collector current of the first transistor is almost equal to a collector current of the second transistor.

However, in this known reference current circuit, a difference collector current is caused by the Early voltage effect in response to a change of the power supply voltage. As a result, it is difficult in the known reference current circuit to prevent the occurrence of a difference base emitter voltage which is caused by the Early voltage effect. Also it is difficult in the known reference current circuit to change the reference current circuit into a reference voltage circuit, and the known reference current circuit has a large current consumption.

Summary of the Invention The invention in its various aspects is defined in the independent claims below, to which reference should now be made. Advantageous features of the invention are set forth in the appendant claims.

This application is divided out of an application No. 9424651.9. Reference to "embodiments of the invention" is to be taken to mean embodiments of the invention of the parent application. The present invention is directed to the circuits of Figures 8, 9, 17 and 18. However it is convenient to retain the description of the other figures to assist the reader in understanding the present invention.

Attention is also drawn to our divisional application No. 97 which is directed to the circuits of Figures 10 and 19.

The circuits described in more detail below with reference to the drawings take the form of reference current or voltage circuits comprising four transistors and two resistors. The first resistor is connected between the base and collector electrodes of the first transistor. The second resistor is connected between the base and collector electrodes of the third transistor.

The emitter electrodes of the first and second transistors are connected to ground. The collector of the first transistor is connected to the base electrode of the second transistor. The base electrode of the first transistor is connected to the collector electrode of the fourth transistor. The collector electrode of the second transistor is connected to the base electrode of the third transistor. The emitter electrodes of the third and fourth transistors are connected to a power supply terminal which is supplied with a power supply voltage.

Each of the first and third transistors has a first emitter area. Each of the second and fourth transistors has an emitter area which is equal to e times as large as the first emitter area, where e represents the base of natural logarithms.

The transistors may comprise four MOS transistors, in which case each of the first and third MOS transistors has a first transconductance, and each of the second and fourth MOS transistors has a transconductance which is equal to four times as large as the first transconductance.

A reference current circuit or a reference voltage circuit embodying the invention can be capable of preventing the occurrence of a difference collector current which is caused by the Early voltage effect in response to a change of a power supply voltage. It is also capable of easily changing the reference current circuit or the reference voltage circuit into the reference voltage circuit or the reference current circuit. It has a small current consumption.

Brief Description of the Drawings: The invention will now be described in more detail, by way of example, with reference to the drawings, in which: Fig. 1 is a circuit diagram of a known reference current circuit; Fig. 2 is a circuit diagram of a reference current circuit according to a first embodiment of this invention; Fig. 3 is a circuit diagram of a part of the reference current circuit illustrated in Fig. 2; Fig. 4 is a graph for use in describing operation of the reference current circuit illustrated in Figs. 2 and 3; Fig. 5 is another graph for use in describing operation of the reference current circuit illustrated in Figs. 2 and 3; Fig. 6 is a circuit diagram of a reference voltage circuit according to a second embodiment of this invention; Fig. 7 is a circuit diagram of a reference voltage circuit according to a third embodiment of this invention; Fig. 8 is a circuit diagram of a reference current circuit according to a fourth embodiment of this invention; Fig. 9 is a circuit diagram of a reference voltage circuit according to a fifth embodiment of this invention; Fig. 10 is a circuit diagram of a reference voltage circuit according to a sixth embodiment of this invention; Fig. 11 is a circuit diagram of a reference current circuit according to a seventh embodiment of this invention; Fig. 12 is a circuit diagram of a part of the reference current circuit illustrated in Fig. 11; Fig. 13 is a graph for use in describing operation of the reference current circuit illustrated in Figs. 11 and 12; Fig. 14 is a graph for use in describing operation of the reference current circuit illustrated in Fig. 11; Fig. 15 is a circuit diagram of a reference voltage circuit according to an eighth embodiment of this invention; Fig. 16 is a circuit diagram of a reference voltage circuit according to a ninth embodiment of this invention; Fig. 17 is a circuit diagram of a reference current circuit according to a tenth embodiment of this invention; Fig. 18 is a circuit diagram of a reference voltage circuit according to an eleventh embodiment of this invention; and Fig. 19 is a circuit diagram of a reference voltage circuit according to a twelfth embodiment of this invention Description of the Preferred Embodiments: Referring to Fig. 1, a known reference current circuit will be described for a better understanding of this invention The known reference current circuit comprises a primary pair of transistors Q21 and Q22 and a secondary pair of transistors Q23 and Ç24 The transistor Q21 has an emitter electrode connected to ground through a resistor R21 The transistor Q22 has an emitter electrode grounded and a base electrode connected to a base electrode of the transistor Q21' The transistor Q23 has an emitter electrode connected to a power supply terminal VCC which is supplied with a power supply voltage from a power supply unit (not shown). The transistor Q23 has a collector electrode connected to a collector electrode of the transistor Q21 The transistor Q24 has an emitter electrode connected to the power supply terminal VCC and a base electrode connected to abase electrode of the transistor Q23. The transistor Q24 has a collector electrode connected to the base electrode of the transistor Q24 and a collector electrode of the transistor Q22' A transistor Q25 has an emitter electrode connected to the power supply terminal Vcc and a base electrode connected to the collector electrode of the transistor Q23 A transistor Q26 has an emitter electrode grounded and a collector electrode connected to a collector electrode of the transistor Q25'- The transistor Q26 has a base electrode connected to the collector electrode of the transistor Q26 and the base electrode of the transistor Q21' The transistor Q21 has an emitter area which is K. times as large as a unit emitter area of a unit transistor. Each of the transistors Q22 to Q24 has an emitter area which is equal to the unit emitter area.

Each of the transistors Q25 and Q26 has an emitter area which is two times as large as the unit emitter area.

Inasmuch as the transistor Q25 has the emitter area which is two times as large as the unit emitter area of the unit transistor, a collector current of the transistor Q21 is almost equal to a collector current of the transistor Q22 It will be assumed that Ici represents a collector current of the unit transistor, VT represents a thermal voltage in an absolute temperature T, Is represents a saturation current in a collector electrode of the unit transistor, K1 represents an emitter area ratio, and VBE represents a base emitter voltage of the transistor. The collector current Ici is given by: Ici = K1 Is exp(VBE/VT) (1) where VT is given by (kT/q), where k represents Boltzman's constant, and q, the charge of a unit electron.

Inasmuch as the transistor Q21 has the emitter area which is K1. times as large as the unit emitter area, a difference base emitter voltage AVBE between the transistors Q21 and Q22 is given by: BE = VBE2 - VBEl = VTln(Kl) = RlIl (2) where VBE1 represents a base emitter voltage of the transistor Q21' VBE2 represents a base emitter voltage of the transistor Q22' and 1 represents a collector current of the transistor Q21' Herein, each of current amplification factors of the transistors Q21 and Q22 is equal to one.

The equation (2) is rewritten by a following equation (3).

VT kT I1 = 1n(K1) = 1n(K1) (3) R1 R1q In this known reference current circuit, the difference base emitter voltage dVBE is caused by Early voltage effect in response to a change of the power supply voltage. As a result, it is hardly possible in the known reference current circuit to prevent occurrence of the difference base emitter voltage dVBE which is caused by Early voltage effect.

It is hardly possible in the known reference current circuit to change the reference current circuit into a reference voltage circuit.

The known reserence current circuit has a large amount of consumption current.

Referring to Figs. 2, 3, 4, and 5, the description will proceed to a reference current circuit according to a first embodiment of this invention.

In Fig. 2, the reference current circuit comprises a pair of first and second transistors Q1 and Q2' a pair of third and fourth transistors Q3 and Q4, and first and second resistors R1 and R2.

The first transistor Q1 has a first emitter electrode grounded and a first emitter area. The second transistor Q2 has a second base electrode connected to a first collector electrode of the first transistor Q1' a second emitter electrode grounded, and a second emitter area. The second emitter area is equal to e times as large as the first emitter area, where e represents the base of natural logarithm.

The third transistor Q3 has a third base electrode connected to a second collector electrode of the second transistor Q2 and a third emitter electrode connected to a power supply terminal VCC The power supply terminal Vcc is supplied with a power supply voltage from a power supply unit (not shown). The third transistor Q3 has a third emitter area which is equal to the first emitter area. The fourth transistor Q4 has a fourth base electrode connected to a third collector electrode of the third transistor Q3 and a fourth collector electrode connected to a first base electrode of the first transistor Q1. The fourth transistor Q4 has a fourth emitter electrode connected to the power supply terminal VCC and a fourth emitter area which is equal to the second emitter area.

The first resistor R1 is connected between the first collector electrode and the first base electrode and has a first resistance value R1. The second resistor R2 is connected between the third collector electrode and the third base electrode and has a second resistance value R2 which is equal to the first resistance value.

A first voltage drop is caused across the first resistor R1 when a first collector current flows in the first resistor R1. A second voltage drop is caused across the second resistor R2 when a second collector current flows in the resistor R2. Each of the first and the second resistors R1 and R2 has a common temperature.

Each of the first and the second voltage drops is substantially equal to a thermal voltage in the common temperature.

The first transistor Q1' the second transistor Q2' and the first resistor R1 are shown in Fig. 3. It will be assumed that I1 represents the first collector current of the first transistor Q1' 12 represents the second collector current of the second transistor Q2, K1 represents an emitter area ratio of the second transistor R2 to the first transistor Q1, VBE1 represents a first base emitter voltage of the first transistor Q1' VBE2 represents a second base emitter voltage of the second transistor Q2, and #VBE represents a difference base emitter voltage between the first and the second base emitter voltages VBE1 and VBE2. The first collector current Ilr the second collector current I2, and the difference base emitter voltage #VBE are given by following equations (4), (5), and (6).

I1 = Is exp(VBE1/VT) (4) 12 = Kl Is exp(VBE2/VT) (5) #VBE = VBE1 - VBE2 = R1I1 (6) A following equation (7) is given by the equations (4), (5), and (6).

I2 = K1 I1 exp(-R1I1/VT) (7) A curved line A in Fig. 4 shows a relation of I1 and I2 in the equation (7). As shown in Fig. 4, I2 has a peak point P1 It will be assumed that K1 is equal to e, where e represents the base of natural logarithm. A following equation (8) is given by the equation (7).

12 e Il exp( -R,I1/VT) (8) A curved line B1 in Fig. -5 shows a relation of Il and 12 in the equation (8). Each of the first and the second transistors Q1 and Q2 is an npn type bipolar transistor. Each of the third and the fourth transistors Q3 and Q4 is a pnp type bipolar transistor. A curved line B2 in Fig. 5 shows a relation of 11 and I2 of the third and the fourth transistors Q3 and Q4. A straight line (I1 = I2) is a line of symmetry of the curved lines B1 and B2. 2 The curved line B1 crosses the curved line B2 at a peak point P1'.

In Fig. 2, it will be assumed that the first resistance value R1 of the first resistor R1 is equal to the second resistance value R2 of the second resistor R2 and each of the first voltage drop across the first resistor R1 and the second voltage drop across the second resistor R2 is substantially equal to the thermal voltage at the absolute temperature T. In this case, each of the first through the fourth transistors Q1 to Q4 has a common operating point which is equal to the peak point P1'. Consequently, when a first change of Il and a second change of I2 are caused by Early voltage effect in response to a change of the power supply voltage, the first change of I1 and the second change of 12 counteract each other. As a result, the reference current circuit is capable of preventing occurrence of a difference collector current of I1 and I 2 Also, the reference current circuit has a consumption current value which is equal to 0.5 times as large as a consumption current value of the known reference current circuit illustrated in Fig. 1.

Referring to Fig. 6, the description will proceed to a reference voltage circuit according to a second embodiment of this invention. Similar parts are designated by like reference numerals.

The reference voltage circuit further comprises a third resistor R3 and a first output voltage terminal T in the reference current circuit illustrated in Fig. 2.

The third resistor R3 is connected between the first base electrode of the first transistor Q1 and the fourth collector electrode of the fourth transistor Q4. The first output voltage terminal T1 is connected to a node of the third resistor R3 and the fourth collector electrode of the fourth transistor Q4. The first output voltage terminal T1 is supplied with a first output voltage VREF1.

On the assumption that I1 = 12, a following equation (9) is given by the equations (4) and (6).

dVBE = VBEl - VTln(Kl) (9) In the reference voltage circuit, the difference base emitter voltage AVBE has a positive temperature characteristic. Also, each of the first and the second base emitter voltages VBE1 and VBE2 has a negative temperature characteristic which is almost equal to -2.3 mV/OC. Consequently, the first output voltage VREF1 may have a positive, negative, or zero temperature characteristic. On the assumption that the second resistance value R2 is approximately equal to twentythree times as large as the first resistance value R1, the first output voltage VREF1 has a zero temperature characteristic.

Referring to Fig. 7, the description will proceed to a reference voltage circuit according to a third embodiment of this invention. Similar parts are designated by like reference numerals.

The reference voltage circuit further comprises a fourth resistor R4 and a second output voltage terminal T2 in the reference voltage illustrated in Fig. 6. The fourth resistor R4 is connected between the second collector electrode of the second transistor Q2 and the third base electrode of the third transistor Q3. The second output voltage terminal T2 is connected to a node of the fourth resistor R4 and the second collector electrode of the second transistor Q2. The second output voltage terminal T2 is supplied with a second output voltage VREF2 The second output voltage VREF2 may have a positive, negative, or zero temperature characteristic which is independent from the temperature characteristic of the first output voltage VREF1. The third and the fourth resistors R3 and R4 have third and fourth resistance values R3 and R4. On the assumption that the third resistance value R4 is approximately equal to twenty-three times as large as the third resistance value R4, the second output voltage VREF2 has a zero temperature characteristic.

Referring to Fig. 8, the description will proceed to a reference current circuit according to a fourth embodiment of this invention. Similar parts are designated by like reference numerals.

A fifth transistor Q5 has a fifth collector electrode connected to the second collector electrode of the second transistor Q27 a fifth emitter electrode connected to the power supply terminal Vcc, and a fifth emitter area which is equal to the first emitter area. A sixth transistor Q6 has a sixth base electrode connected to a fifth base electrode of the fifth transistor Q5, a sixth collector electrode connected to the first base electrode of the first transistor Q1' a sixth emitter electrode connected to the power supply terminal Vcc, and a sixth emitter area which is equal to the first emitter area.

A seventh transistor Q7 has a seventh emitter electrode connected to the power supply terminal VCCJ a seventh base electrode connected to the fifth base electrode of the fifth transistor Q5, and a seventh collector electrode connected to the seventh base electrode. An eighth transistor Q8 has an eighth emitter electrode grounded, an eighth base electrode connected to the second collector electrode of the second transistor Q2' and an eighth collector connected to the seventh collector elettrode of the seventh transistor Q7.

A ninth transistor Qg has a ninth emitter electrode connected to the power supply terminal Vcc, a ninth base electrode connected to the seventh base electrode of the second terminal Q7, and a ninth emitter electrode connected to an output current terminal To which is supplied with an output current Io. The ninth transistor Qg has a ninth emitter area which is equal to the first emitter area. A tenth transistor Q10 has a tenth emitter electrode grounded, a tenth base electrode connected to the eighth base electrode of the eighth transistor Q87 and a tenth collector electrode connected to an input current terminal Ti which is supplied with an input current Ii.

With this structure, on the assumption that I1 = 12, the first collector current I1 is given by a following equation (10).

VT kT I = - ln(K) = - ln(K) (10) R1 Rlq Consequently, the first and the second collector currents I1 and 12 are proportional to the absolute temperature T. As a result, the reference current circuit has a positive temperature characteristic.

Inasmuch as the first and the second collector currents 1 and I2 are controlled by the seventh and the eighth transistors Q7 and Q8, the first and the second collector currents I1 and I2 are held at a constant current value even when the power supply voltage is changed.

Referring to Fig. 9, the description will proceed to a reference voltage circuit according to a fifth embodiment of this invention. Similar parts are designated by like reference numerals.

A fifth resistor R5 is connected between the first base electrode of the first transistor and the sixth collector electrode of the sixth transistor Q6. The fifth resistor R5 has a fifth resistance value R5. A third output voltage terminal T3 is connected to a node of the fifth resistor R5 and the sixth collector electrode of the sixth transistor Q6. The third output voltage terminal T3 is supplied with a third output voltage VREF3. A sixth resistor R6 is connected between the second collector electrode of the second transistor Q2 and the fifth collector electrode of the fifth transistor Q5. The sixth resistor R6 has a sixth resistance value R6 which is equal to the fifth resistance value R5 of the fifth resistor R5. The third output voltage VREF3 is given by: R5 VREF3 = VBE1 + R5I1 = VBE1 + #VBE R1 RS = VBEl + - VTlntK) (11) Rl Inasmuch as the first and the second collector currents I1 and I2 are proportional to the absolute temperature T, the difference base emitter voltage #VBE is proportional to the absolute temperature T. The difference base emitter voltage #VBE has a positive temperature characteristic. On the other hand, the first base emitter voltage VBE1 has a negative temperature characteristic which is, for example, approximately equal to -2 mV/ C. As a result, the third output voltage VREF3 may have a positive, negative, or zero temperature characteristic.

Referring to Fig. 10, the description will proceed to a reference voltage circuit according to a sixth embodiment of this invention. Similar parts are designated by like reference numerals.

The second transistor Q2 has the second base electrode connected to the first base electrode of the first transistor Q1. The fifth transistor Q5 has the fifth collector electrode connected to the second collector electrode of the second transistor Q2. The sixth transistor Q6 has the sixth collector electrode connected to the sixth base electrode of the sixth transistor Q6.

An eleventh transistor Q11 has an eleventh base electrode connected to the fifth collector electrode, an eleventh emitter electrode connected to the power supply terminal Vcc, and an eleventh emitter area which is equal to two times as large as the first emitter area. A twelfth transistor Q12 has a twelfth base electrode connected to the second base electrode of the second transistor Q2, a twelfth collector electrode connected to the twelfth base electrode, and a twelfth emitter electrode grounded. The twelfth transistor Q12 has a twelfth emitter area which is equal to the eleventh emitter area.

A seventh resistor R7 is connected between ground and the second emitter electrode of the second transistor Q2. The seventh resistor R7 has a seventh resistance value R7. An eighth resistor R8 is connected between an eleventh collector electrode of the eleventh transistor Qll and a twelfth collector electrode of the twelfth transistor Q12. The eighth resistor R8 has an eighth resistance value R8. A fourth ouput voltage terminal T4 is connected to a node of the eighth resistor R8 and the eleventh collector electrode of the eleventh transistor Q11' The fourth output voltage terminal T4 is supplied with a fourth output voltage VREF4 It will be assumed that the twelfth transistor Q12 has a twelfth base emitter voltage VBE12 and AVBE represents a difference base emitter voltage between the second and the twelfth base emitter voltages VBE2 and VBE12 The fourth output voltage VREF4 is given by: R3 VREF4 = VBE12 + 2R8I2 = VBE12 + 2 #VBE R7 R8 = VBEl + 2 - Vln(K) (12) R7 The difference base emitter voltage #VBE has a positive temperature characteristic. On the other hand, the twelfth base emitter voltage VBE12 has a negative temperature characteristic. As a result, the fourth output voltage VREF4 may have a positive, negative, or zero temperature characteristic.

Referring to Figs. 11, 12, and 13, the description will proceed to a reference current circuit according to a seventh embodiment of this invention.

The reference current circuit comprises a plurality of metal oxide semiconductor (MOS) field effect transistors (FET) which will hereafter be called MOS transistors.

In Fig. 11, the reference current circuit comprises a pair of first and second MOS transistors M1 and M2, a pair of third and fourth MOS transistors M3 and M4, and the first and the second resistors R1 and R2.

The first MOS transistor M1 has a first source electrode grounded and a first transconductance. The second MOS tra transistor M1, a second source electrode grounded, and a second transconductance. The second transconductance is equal to four times as large as the first transconductance.

The third MOS transistor M3 has a third gate electrode connected to a second drain electrode of the second MOS transistor M2 and a third source electrode connected to a power supply terminal VDD The power supply terminal VDD is supplied with a power supply voltage from a power supply unit (not shown). The third MOS transistor M3 has a third transconductance which is equal to the first transconductance. The fourth MOS transistor M4 has a fourth gate electrode connected to a third drain electrode of the third MOS transistor M3 and a fourth drain electrode connected to a first gate electrode of the first MOS transistor M1. The fourth MOS transistor M4 has a fourth source electrode connected to the power supply terminal VDD and a fourth transconductance which is equal to the second transconductance.

The first resistor R1 is connected between the first drain electrode and the first gate electrode and has a first resistance value R1. The second resistor R2 is connected between the second drain electrode and the second gate electrode and has a second resistance value R2 which is equal to the first resistance value. The transconductance is approximately equal to a gate (L/W) ratio.

A first voltage drop is caused across the first register R1 when a first drain current flows in the first resistor R1. A second voltage drop is caused across the second resistor R2 when a second drain current flows in the resistor R2. Each of the first and the second resistors R1 and R2 has a common temperature. Each of the first and the second voltage drops is substantially equal to a thermal voltage in the common temperature.

The MOS transistor may be operated in a saturation area. It is assumed that the MOS transistor has n channels and a transconductance ssn. In this event, a drain current IDi is given by a following equation (13) in the saturation area of the MOS transistor.

IDi = Kjssn(VGSi - VTH) (13) where K. represents an ability ratio or transconductance ratio to a unit MOS transistor, VGSi represents a gate source voltage, VTH represents a threshold voltage, Sn is given by EAn(C.ox/2)(W/L)37 )1n represents an effective mobility of carrier, C represents a capacity of gate oxide film per unit area, W represents a width of gate electrode, and L represents a length of gate electrode.

The first MOS transistor M1, the second MOS transistor M2, and the first resistor R1 are shown in Fig. 12. It will be assumed that ID1 represents the first drain current of the first MOS transistor M1, ID2 represents the second drain current of the second MOS transistor M2, K2 represents a transconductance ratio of the second MOS transistor M2 to the first MOS transistor M1, VGSl represents a first gate source voltage of the first MOS transistor M1, VGS2 represents a second gate source voltage of the second MOS transistor M2, and AVGS represents a difference gate source voltage between the first and the second gate source voltages VGS1 and VGS2.

The first drain current ID1, the second drain current ID2, and the difference gate source voltage #VGS are given by following equations (14), (15), and (16).

ID1 = ssn(VGS1 - VTH) (14) ID2 = K2ssn(VGS2 - VTH) (15) #VGS = VGS1 - VGS2 = ID1R1 (16) A following equation (17) is given by the equations (14), (15), and (16).

where ID1 is given by [ID1#1/(R1ssn)] A curved line C in Fig.l3 shows a relation of 1Dl and ID2 in the equation (17). As shown in Fig. 13, ID2 has a peak point P2.

On the assumption that (dID2/dIl) = 0 in the equation (17), ID1 is given by a following equation (18).

ID1 = 1/(R1ssn), R1ssn (18) Consequently, a peak value ID2P of the drain current ID2 is given by a following equation (19).

D2P = 1/(16R1ssn) = (K2/4)ID1 (19) In Fig. 11, it will be assumed that K2 is equal to four, the first resistance value R1 of the first resistor R1 is equal to the second resistance value R2 of the second resistor R27 and each of the first voltage drop across the first resistor R1 and the second voltage drop across the second resistor R2 is substantially equal to the thermal voltage in the absolute temperature T. In this case, each of the first through the fourth MOS transistors M1 to M4 has a common operating point which is equal to the peak point P2. Consequently, when a first change of ID1 and a second change of ID2 are caused by Early voltage effect in response to a change of the power supply voltage, the first change of ID1 and the second change of ID2 counteract each other. As a result, the reference current circuit is capable of preventing occurrence of a difference drain current of 1D1 and ID2.

The transconductance /3n is given by a following equation (20).

ssn = ss0(T/To) (20) where 73o represents a transconductance in a temperature (300 K). A relation of (l/pn) ) and an absolute 0 1/3n an temperature T is shown in Fig. 14.

A differential temperature coefficient [TCF(ssn)] of ssn in the temperature (300 K) is equal to -5,000 ppm/ C. A differential temperature coefficient [TCF(VT)] of VT is positive. The differential temperature coefficient [TCF(ssn)] is negative and an absolute value which is equal to 1.5 times as large as an absolute value of the differential temperature coefficient [TCF(VT)].

As shown in the equations (18) and (19), each of the drain currents 1D1 and ID2 is proportional to Consequently, a differential temperature coefficient [TCF(1/ssn)] is equal to 5,000 ppm/ C in the temperature (330 K).

Referring to Fig. 15, the description will proceed to a reference voltage circuit according to an eighth embodiment of this invention. Similar parts are designated by like reference numerals.

The reference voltage circuit further comprises the third resistor R3 and the first output voltage terminal T1 in the reference current circuit illustrated in Fig. 11. The third resistor R3 is connected between the first gate electrode of the first MOS transistor M1 and the fourth drain electrode of the fourth MOS transistor M4. The first output voltage terminal T1 is connected to the node of the third resistor R3 and the fourth drain electrode of the fourth MOS transistor M4.

The first output voltage terminal T1 is supplied with a first output voltage VREF1.

On the assumption that ID1 = ID2, a following equation (21) is given VREF1 = VGS1 + ID1R2 1 R2 = (1 + -) + V (21) 2Rlssn 2R1 On the assumption that VTH =. 0.7V, VTH has a temperature characteristic which is approximately equal to -2.3 mv/ C. Also, a voltage drop (I1R1) has a positive temperature characteristic. Consequently, the first output voltage VREF1 may have a positive, negative, or zero temperature characteristic.

Referring to Fig. 16, the description will proceed to a reference voltage circuit according to a ninth embodiment of this invention. Similar parts are designated by like reference numerals.

The reference voltage circuit further comprises the fourth resistor R4 and the second output voltage terminal T2 in the reference voltage illustrated in FIg.

15. The fourth resistor R4 is connected between the second drain electrode of the second MOS transistor M2 and the third gate electrode of the third MOS transistor M3. The second output voltage terminal T2 is connected to the node of the fourth resistor R4 and the second drain electrode of the second MOS transistor M2. The second output voltage terminal T2 is supplied with the second output voltage VREF2. The second output voltage VREF2 may have a positive, negative, or zero temperature characteristic which is independent relative to the temperature characteristic of the first output voltage VREF1, The third and the fourth resistors R3 and R4 have third and fourth resistance values R3 and R4.

Referring to Fig. 17, the description will proceed to a reference current circuit according to a tenth embodiment of this invention. Similar parts are designated by like reference numerals.

A fifth MOS transistor M5 has a fifth drain electrode connected to the second drain electrode of the second MOS transistor M2, a fifth source electrode connected to the power supply terminal VDD, and a fifth trans conductance which is equal to the first transconductance. A sixth MOS transistor M6 has a sixth gate electrode connected to a fifth gate electrode of the fifth MOS transistor MS, a sixth drain electrode connected to the first gate electrode of the first MOS transistor M1, a sixth source electrode connected to the power supply terminal VDD, and a sixth transconductance which is equal to the first transconductance A seventh MOS transistor M7 has a seventh source electrode connected to the power supply terminal VDD, a seventh gate electrode connected to the fifth gate electrode of the fifth MOS transistor MS, and a seventh drain electrode connected to the seventh gate electrode.

An eighth MOS transistor M8 has an eighth source electrode grounded, an eighth gate electrode connected to the second drain electrode of the second MOS transistor M2, and an eighth drain electrode connected to the seventh drain electrode of the seventh MOS transistor M7.

A ninth MOS transistor Mg has a ninth source electrode connected to the power supply terminal VDD, a ninth gate electrode connected to the seventh gate electrode of the seventh MOS transistor M7, and a ninth source electrode connected to the output current terminal To which is supplied with the output current lo. The ninth MOS transistor Mg has a ninth transconductance which is equal to the first transconductance. A tenth MOS transistor Mlo has a tenth source electrode grounded, a tenth gate electrode connected to the eighth gate electrode of the eighth MOS transistor M8, and a tenth drain electrode connected to the input current terminal Ti which is supplied with the input current Ii.

Inasmuch as the first and the second drain currents ID1 and ID2 are controlled by the seventh and the eighth MOS transistors M7 and M8, the first and the second drain currents ID1 and ID2 are held at a constant current value even when the power supply voltage is changed.

Referring to Fig. 18, the description will proceed to a reference voltage circuit according to an eleventh embodiment of this invention. Similar parts are designated by like reference numerals.

The fifth resistor R5 is connected between the first gate drain electrode of the first MOS transistor M1 and the sixth drain electrode of the sixth MOS transistor M6. The fifth resistor R5 has a fifth resistance value R5. A third output voltage terminal T3 is connected to a node of the fifth resistor R5 and the sixth drain electrode of the sixth MOS transistor M6. The third output voltage terminal T3 is supplied with a third output voltage VREF3 The sixth resistor R6 is connected between the second drain electrode of the second MOS transistor M2 and the fifth drain electrode of the fifth MOS transistor M5. The sixth resistor R6 has a sixth resistance value R6 which is equal to the fifth resistance value R5 of the fifth resistor R5. The third output voltage VREF3 is given by: R5 VREF3 = VGS1 + R5ID1 = VGS1 + #VGS R1

As illustrated in the equation (2:2), the third output voltage VREF3 may have a positive, negative, or zero temperature characteristic.

Inasmuch as the first and the second drain currents ID1 and ID2 are controlled by the seventh and the eighth MOS transistors M7 and M8, the first and the second drain currents ID1 and ID2 are held at the constant value even when the power supply voltage is changed.

Referring to Fig. 19, the description will proceed to a reference voltage circuit according to a twelfth embodiment of this invention. Similar parts are designated by like reference numerals.

The second MOS transistor M2 has the second gate electrode connected to the first gate electrode of the first MOS transistor M1. The fifth MOS transistor M5 has the fifth drain electrode connected to the second drain electrode of the second MOS transistor M2. The sixth MOS transistor M6 has the sixth drain electrode connected to the sixth gate electrode of the sixth MOS transistor M6.

The eleventh MOS transistor M11 has an eleventh gate electrode connected to the fifth drain electrode, an eleventh source electrode connected to the power supply terminal VDD, and an eleventh transconductance which is equal to the first transconductance. A twelfth MOS transistor N12 has a twelfth gate electrode connected to the second gate electrode of the second MOS transistor M2, a twelfth drain electrode connected to the twelfth gate electrode, and a twelfth source electrode grounded.

The twelfth MOS transistor M12 has a twelfth transconductance which is equal to the eleventh transconductance.

The seventh resistor R7 is connected between ground and the second source electrode of the second MOS transistor M2. The seventh resistor R7 has a seventh resistance value R7. The eighth resistor R8 is connected between an eleventh drain electrode of the eleventh MOS transistor M11 and a twelfth drain electrode of the twelfth MOS transistor M12. The eighth resistor R8 has an eighth resistance value R8. The fourth output voltage terminal T4 is connected to a node of the eighth resistor R8 and the eleventh drain electrode of the eleventh MOS transistor Mull. The fourth output voltage terminal T4 is supplied with a fourth output voltage VREF4 It will be assumed that the twelfth MOS transistor M12 has a twelfth gate source voltage VEGS12 and dVGS represents a difference gate source voltage between the second and the twelfth gate source voltages VGS2 and VGSl2.

Inasmuch as a twelfth drain current ID12 is the first or the second drain current ID1 or ID2, the twelfth drain current ID12 is given by a following equation (23).

ID12 = ssn(VGS1 - VTH) (23) Also, VGSl2 is given by a following equation (24).

#VGS12 = VGS1 - VGS2 = R1ID2 (24) A following equation (2.5) is given by the equations (14), (15), (23), and (24).

1 1 ID1 = ID2 = ID12 = (1 - ) (25) ssR1 #K2 Also, the fourth output voltage VREF4 is given by a following equation (26).

VREF4 = VGS12 + R8ID12 = VGS1 + R8 #GVS12 R7

As illustrated in the equation (26), the fourth output voltage VREF4 may have a positive, negative, or zero temperature characteristic.

Claims

1. A reference current circuit comprising: a primary pair of first and second transistors, said first transistor having a first emitter electrode grounded and a first emitter area, said second transistor having a second base electrode connected to a first collector electrode of said first transistor, a second emitter electrode grounded, and a second emitter area which is equal to e times as large as said first emitter area, where e represents the base of natural logarithm.

a secondary pair of third and fourth transistors, said third transistor having a third collector electrode connected to a second collector electrode of said second transistor, a third emitter electrode connected to a power supply terminal which is supplied with a power supply voltage, and a third emitter area which is equal to said first emitter area, said fourth transistor having a fourth base electrode connected to a third base electrode of said third transistor, a fourth collector electrode connected to a first base electrode of said first transistor, a fourth emitter electrode connected to said power supply terminal, and a fourth emitter area which is equal to said first emitter area; a resistor connected between said first collector electrode and said first base electrode; a fifth transistor having a fifth emitter electrode connected to said power supply terminal, a fifth base electrode connected to said third base electrode, and a fifth collector electrode connected to said fifth base electrode; and a sixth transistor having a sixth emitter electrode grounded, a sixth base electrode connected to said second collector electrode, and a sixth collector electrode connected to said fifth collector electrode.

2. A reference current circuit as claimed in Claim 1, wherein a voltage drop is caused across said resistor which has a temperature, said voltage drop being substantially equal.

3. A reference voltage circuit comprising: a primary pair of firs and second transistors, said first transistor having a first emitter electrode grounded and a first emitter area, said second transistor having a second base electrode connected to a first collector electrode of said first transistor, a second emitter electrode grounded, and a second emitter area which is equal to e times as large as said first emitter area, where e represents the base of natural logarithm; a secondary pair of third and fourth transistors, said third transistor having a third emitter electrode connected to a power supply terminal which is supplied with a power supply voltage, and a third emitter area which is equal to said first emitter area, said fourth transistor having a fourth base electrode connected to a third base electrode of said third transistor, a fourth emitter electrode connected to said power supply terminal, and a fourth emitter area which is equal to said first emitter area; a first resistor connected between said first collector electrode and said first base electrode; a second resistor connected between said first base electrode and a fourth collector electrode of said fourth transistor, said second resistor having a primary resistance value; an output voltage terminal connected to a node of said fourth collector electrode of said fourth transistor and said second transistor; a third resistor connected between a second collector electrode of said second transistor and a third collector electrode of said third transistor, said third resistor having a secondary resistance value which is equal to said primary resistance value; a fifth transistor having a fifth emitter electrode connected to said power supply terminal, a fifth base electrode connected to said third base electrode, and a fifth collector electrode connected to said fifth base electrode; and a sixth transistor having a sixth emitter electrode grounded, a sixth base electrode connected to said second collector electrode, and a sixth collector electrode connected to said fifth collector electrode.

4. A reference voltage circuit as claimed in Claim 3, wherein a voltage drop is caused across said first resistor which has a temperature, said voltage drop being substantially equal.

5. A reference current circuit comprising: a primary pair of first and second MOS transistors, said first MOS transistor having a first source electrode grounded and a first transconductance, said second MOS transistor having a second gate electrode connected to a first drain electrode of said first MOS transistor, a second source electrode grounded, and a second transconductance which is equal to four times as large as said first transconductance; a secondary pair of third and fourth MOS transistors, said third MOS transistor having a third drain electrode connected to a second drain electrode of said second MOS transistor, a third source electrode connected to a power supply terminal which is supplied with a power supply voltage, and a third transconductance which is equal to said first transconductance, said fourth MOS transistor having a fourth gate electrode connected to a third gate electrode of said third MOS transistor, a fourth drain electrode connected to a first gate electrode of said first MOS transistor, a fourth source electrode connected to said power supply terminal, and a fourth transconductance which is equal to said first transconductance; a resistor connected between said first drain electrode and said first gate electrode; a fifth MOS transistor having a fifth source electrode connected to said power supply terminal, a fifth gate electrode connected to said third gate electrode, and a fifth drain electrode connected to said fifth gate electrode; and a sixth MOS transistor having a sixth source electrode grounded, a sixth gate electrode connected to said second drain electrode, and a sixth drain electrode connected to said fifth drain electrode.

6. A reference current circuit as claimed in Claim 5, wherein a voltage drop is caused across said resistor which has a temperature, said voltage drop being substantially equal.

7. A reference voltage circuit comprising: a primary pair of first and second MOS transistors, said first MOS transistor having a first source electrode grounded and a first transconductance, said second MOS transistor having a second gate electrode connected to a first drain electrode of said first MOS transistor, a second source electrode grounded, and a second transconductance which is equal to four times as large as said first transcondu-ctance; a secondary pair of third and fourth MOS transistors, said third MOS transistor having a third source electrode connected to a power supply terminal which is supplied with a power supply voltage, and a third trans conductance which is equal to said first transconductance, said fourth MOS transistor having a fourth gate electrode connected to a third gate electrode of said third MOS transistor, a fourth source electrode connected to said power supply terminal, and a fourth transconductance which is equal to said first trans conductance; a first resistor connected between said first drain electrode and said first base electrode; a second resistor connected between said first gate electrode and a fourth drain electrode of said fourth MOS transistor, said second resistor having a primary resistance value; an output voltage terminal connected to a node of said fourth drain electrode of said fourth MOS transistor and said second resistor; a third resistor connected between a second drain electrode of said second MOS transistor and a third drain electrode of said third MOS transistor, said third resistor having a secondary resistance value which is equal to said primary resistance value; a fifth MOS transistor having a fifth source electrode connected to said power supply terminal, a fifth gate electrode connected to said third gate electrode, and a fifth drain electrode connected to said fifth gate electrode; and a sixth MOS transistor having a sixth source electrode grounded, a sixth gate electrode connected to said second drain electrode, and a sixth drain electrode connected to said fifth drain electrode.

8. A reference voltage circuit as claimed in Claim 7, wherein a voltage drop is caused across said first resistor which has a temperature, said voltage drop being substantially equal.