CN1702589A - Current source with very high output impedance - Google Patents

Abstract

A current source provided with high output impedance comprises a current source-generating circuit and a equivalent negative resistance generating circuit, wherein, the said current source-generating circuit can comprise all the current source circuit such as Cascode, Wilson, or Widlar current mirror and so on to generate positive resistance and reference current; the said negative resistance generating circuit comprises a short-circuit grid-drip POMS pipe, a NMOS pipe and an amplifier to generate equivalent negative resistance whose absolute value is made larger than the former one through designing; then the said equivalent negative resistance is connected in parallel with the said positive resistance to get super high output resistance whose value is close to 109 ohm magnitude order.

Description

A kind of current source with high output impedance

Technical field

The invention belongs to electronic technology field, be specifically related to the current source technology in the integrated circuit fields.

Background technology

Current source is a kind of variation with its terminal voltage, and its output current keeps constant circuit, and it is the important composition part in the Analogous Integrated Electronic Circuits, and demand is widely arranged in Analogous Integrated Electronic Circuits.For electric current, not loss on long metal wire, voltage then has loss, so in having the complicated mimic channel of long metal wire, current source is more welcome.U.S. John Wiley﹠amp; " the Analysis and Design of Analog IntegratedCircuits " (4 that writes by people such as Paul R.Gray that Sons company calendar year 2001 publishes ^ThEdition) chapter 4 has been introduced various types of current sources, and as this book was described, current source both can be made biasing element, also can serve as the active load of amplifier stage.Wherein, the output impedance of current source is the important parameter of current source circuit, and output impedance is high more, shows that the current source output current is stable more.Therefore, in the high precision integrated circuit, the design in high impedance current source is extremely important.And owing to being of wide application of contemporary electronic systems, environment is harsher, therefore requires current source can both work reliably in very wide temperature range (25 ℃～125 ℃) and very wide supply voltage range circuit.

Common current source circuit, its output impedance are about the megohm order of magnitude, and its electric current output is stable inadequately.In order to improve current source output impedance, conventional method is at current source output impedance r ₀High resistance measurement r of last polyphone ₁, make total output impedance R _Out=r ₀+ r ₁(as shown in Figure 1).But can consume bigger voltage remaining like this, simultaneously, need higher supply voltage.

Actual current source circuit exists some problems, such as output impedance is big inadequately, and stable output current need could realize under high voltage etc.

Summary of the invention

The objective of the invention is to propose a kind of current source, simultaneously this current source less minimum output voltage that makes outputting current steadily (Vomin) that should have, well current stability and frequency response characteristic and very little temperature coefficient with high output impedance.

A kind of current source that the present invention proposes with high output impedance, comprise an electric current source generating circuit, it is characterized in that it comprises that also an equivalent negative resistance produces circuit, described equivalent negative resistance generation circuit and electric current source generating circuit are in parallel and produce high output impedance.Wherein, the electric current source generating circuit is used to produce a positive resistance and a reference current; Equivalent negative resistance produces circuit and is used to produce an equivalent negative resistance.Described electric current source generating circuit can be realized with all current source circuits.

The structure that technical scheme of the present invention comes down to utilize two very close positive negative resistances of absolute value to be in parallel realizes the high output impedance of current source.The positive output impedance of supposing the electric current source generating circuit is r ₀, the equivalent negative resistance that equivalent negative resistance produces circuit is r ₂, then total output impedance after two circuit parallel connections $R_{\mathrm{out}}=\frac{r_o{r}_2}{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="A20051002112200152.png,A20051002112200172.png"\; state="\{\{state\}\}">r</figure-callout>}}_0+{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20051002112200151.png,A20051002112200152.png"\; state="\{\{state\}\}">r</figure-callout>}}_2},$ By suitable calculating, be provided with | r ₂| be slightly larger than | r ₀|, just can obtain high output impedance R _OutCurrent source.

Wherein, producing the electric current source generating circuit of positive resistance and reference current, can be all current source circuits such as Cascode current mirror, Wilson current mirror or Widlar current source.

If use the Cascode current mirror, then the electric current source generating circuit comprises:

(1) current reference source Iref1 is used to produce steady current, and one end and external power supply join, and the drain electrode of the other end and NMOS pipe M3 is joined.

(2) four NMOS pipe (M1, M2, M3 and M4) is used to produce the image current of Iref1.NMOS pipe M1 and M2 constitute mirrored transistor, and NMOS pipe M3 and M4 constitute mirrored transistor.The source ground of the nmos pass transistor of two mirror images (M1 and M2) wherein, its grid is connected to each other, and is connected to the drain electrode of NMOS pipe M1, and the source electrode of NMOS pipe M3 is received in the drain electrode of NMOS pipe M1, and the source electrode of NMOS pipe M4 is received in the drain electrode of NMOS pipe M2; The grid of the NMOS pipe (M3 and M4) of two other mirror image interconnects, and is connected to the drain electrode of NMOS pipe M3, and the drain electrode of NMOS pipe M3 connects additional power source by current reference source Iref1.

If use the Wilson current mirror, then the electric current source generating circuit comprises:

(1) current reference source Iref1 is used to produce steady current, and one end and external power supply join, and the drain electrode of the other end and NMOS pipe M3 is joined.

(2) four NMOS pipe (M1, M2, M3 and M4) is used to produce the image current of Iref1.NMOS pipe M1 and M2 constitute mirrored transistor, and NMOS pipe M3 and M4 constitute mirrored transistor.The source ground of the nmos pass transistor of two mirror images (M1 and M2) wherein, its grid is connected to each other, and is connected to the drain electrode of NMOS pipe M2, and the source electrode of NMOS pipe M3 is received in the drain electrode of NMOS pipe M1, and the source electrode of NMOS pipe M4 is received in the drain electrode of NMOS pipe M2; The grid of the NMOS pipe (M3 and M4) of two other mirror image interconnects, and is connected to the drain electrode of NMOS pipe M3, and the drain electrode of NMOS pipe M3 connects additional power source by current reference source Iref1.

If use the Widlar current source, then the electric current source generating circuit comprises:

(1) two nmos pass transistor (M1 and M2) and two resistance (R1 and R2), the grid of two NMOS pipes is connected to each other, and is connected to the drain electrode of NMOS pipe M1, the source ground of NMOS pipe M1, the drain electrode of NMOS pipe M1 is connected with external power supply by resistance R 1; The source electrode of NMOS pipe M2 is connected with ground by resistance R 2.

Equivalent negative resistance of the present invention produces circuit and comprises:

(1) PMOS pipe M5, the grid of PMOS pipe M5 and drain electrode short circuit, its drain electrode is connected on the drain electrode of NMOS pipe M6.

(2) NMOS pipe M6 are used for providing bias current to PMOS pipe M5.The grid of NMOS pipe M6 meets biasing voltage signal Vbias1, and its source electrode is connected with ground, and the drain electrode of NMOS pipe M6 is connected with the drain electrode of NMOS pipe M5.

(3) voltage gains are slightly larger than 1 amplifier, and the source electrode of its input end and PMOS pipe M5 joins, and output terminal joins with grid and drain electrode that PMOS manages M5.

This amplifier can be cmos amplifier (A1), comprising:

The first order of a PMOS pipe M7 and a NMOS pipe M10 formation amplifier is used for that signal is carried out the first order and amplifies; The second level of a PMOS pipe M11 and a NMOS pipe M8 formation amplifier is used for that signal is carried out the second level and amplifies; Two NMOS pipes (M9 and M12) constitute the third level of amplifier; The grid of PMOS pipe M7 is as the input end of cmos amplifier A1, and its source electrode and additional power source join, and its drain electrode is joined with the grid that NMOS manages M8; NMOS manages the grid and drain electrode short circuit of M10, and joins with the drain electrode of PMOS pipe M7, and the source electrode of NMOS pipe M10 is connected with ground; The grid of PMOS pipe M11 and drain electrode short circuit, and join with the drain electrode of NMOS pipe M8 and the grid of NMOS pipe M9 simultaneously; The grid of NMOS pipe M8 joins with the drain electrode of PMOS pipe M7 and the drain electrode of NMOS pipe M10 simultaneously, and the drain electrode of NMOS pipe M8 is joined with the drain electrode of PMOS pipe M11 and the grid of NMOS pipe M9 simultaneously, and the source electrode of NMOS pipe M8 is connected with ground; The source electrode of NMOS pipe M9 is connected with the drain electrode of NMOS pipe M12, and drain electrode and the additional power source of NMOS pipe M9 join; The grid of NMOS pipe M12 meets biasing voltage signal Vbias1, and the source electrode of NMOS pipe M12 joins with ground.

Equivalent negative resistance generation circuit of the present invention is in parallel with the electric current source generating circuit and is connected, to produce the high output impedance of whole current source.Its concrete annexation is:

1, if the electric current source generating circuit is the Cascode current mirror, then the annexation of the two is: the drain electrode of NMOS pipe M4 links to each other with the source electrode of PMOS pipe M5 and the grid of PMOS pipe M7 simultaneously; The output terminal of whole current source is the drain electrode of NMOS pipe M4, the source electrode of PMOS pipe M5 and the common tie point that PMOS manages the grid of M7.

2, if the electric current source generating circuit is the Wilson current mirror, then the annexation of the two is: the drain electrode of NMOS pipe M4 links to each other with the source electrode of PMOS pipe M5 and the grid of PMOS pipe M7 simultaneously; The output terminal of whole current source is the drain electrode of NMOS pipe M4, the source electrode of PMOS pipe M5 and the common tie point that PMOS manages the grid of M7.

3, if the electric current source generating circuit is the Widlar current source, then the annexation of the two is: the drain electrode of NMOS pipe M2 links to each other with the source electrode of PMOS pipe M5 and the grid of PMOS pipe M7 simultaneously; The output terminal of whole current source is the drain electrode of NMOS pipe M2, the source electrode of PMOS pipe M5 and the common tie point that PMOS manages the grid of M7.

Need to prove that the equivalent negative resistance described in the present invention is not made of special material or device, but realize by common amplifier circuit and MOS transistor.

A kind of current source circuit with high output impedance of the present invention has the following advantages:

1, greatly improved the output impedance of current source, its output impedance can reach 10 ⁹The ohmage magnitude, thus make output current more stable with the variation of its output voltage.

2, improved Vomin, made output current under lower voltage, just can reach stable.As shown in Figure 9, do not add the Vomin ≈ 2.100V (curve 5) that equivalent negative resistance produces the single Cascode current mirror of circuit; But after adding equivalent negative resistance generation circuit, the Vomin of current source of the present invention has reduced, Vomin ≈ 1.465V (curve 4).As shown in figure 10, do not add the Vomin ≈ 2.105V (curve 7) that equivalent negative resistance produces the single Wilson current mirror of circuit; But after adding equivalent negative resistance generation circuit, the Vomin of current source of the present invention has reduced, Vomin ≈ 1.483V (curve 6).

3, electric current source generating circuit of the present invention can be made of all current source circuits such as common Cascode current mirror, Wilson current mirror or Widlar current sources, and simple in structure, chip occupying area is little, and power consumed is low.

4, the high output impedance circuit structure of the present invention's proposition makes the outputting current steadily of current source fine, and its frequency response characteristic is good.

5, the temperature coefficient of the output current of the high output impedance current source of the present invention's proposition is very little, and temperature coefficient (40 ℃～+ 145 ℃) in very wide range of temperature is 10.6ppm/ ℃.

Description of drawings:

Fig. 1 is the method synoptic diagram of the raising current source output impedance of routine.

Fig. 2 is a kind of structured flowchart with current source of high output impedance of the present invention.

Fig. 3 is the current source circuit schematic diagram with high output impedance that a kind of Cascode of utilization current mirror is made the electric current source generating circuit.

Fig. 4 is the current source circuit schematic diagram with high output impedance that a kind of Wilson of utilization current mirror is made the electric current source generating circuit.

Fig. 5 is the current source circuit schematic diagram with high output impedance that a kind of Widlar of utilization current source is made the electric current source generating circuit.

Fig. 6 is the circuit diagram that equivalent negative resistance produces a kind of cmos amplifier A1 in the circuit.

Fig. 7 is the relation curve of the output current of a kind of Cascode of utilization current mirror current source with high output impedance of making the electric current source generating circuit with output voltage.Curve 1 is the relation of the electric current of current reference source Iref1 with output voltage, and curve 2 is the relation of output current of the present invention with output voltage.

Fig. 8 is the relation curve of the output current of a kind of Wilson of utilization current mirror current source with high output impedance of making the electric current source generating circuit with output voltage.Curve 1 is the relation of the electric current of current reference source Iref1 with output voltage, and curve 3 is the relation of output current of the present invention with output voltage.

Fig. 9 is the comparison of the Vomin of the Vomin of output current of a kind of Cascode of utilization current mirror current source with high output impedance of making the electric current source generating circuit and single Cascode current mirror output current.Wherein, curve 5 is the output current of single Cascode current mirror, and curve 4 is the output current of current source of the present invention.

Figure 10 is the comparison of the Vomin of the Vomin of output current of a kind of Wilson of utilization current mirror current source with high output impedance of making the electric current source generating circuit and single Wilson current mirror output current.Wherein, curve 7 is the output current of single Wilson current mirror, and curve 6 is the output current of current source of the present invention.

Figure 11 is the temperature characteristics of the output current of a kind of Cascode of utilization current mirror current source with high output impedance of making the electric current source generating circuit.

Figure 12 is the temperature characteristics of the output current of a kind of Wilson of utilization current mirror current source with high output impedance of making the electric current source generating circuit.

Figure 13 is the frequency characteristic of the output current of a kind of Cascode of utilization current mirror current source with high output impedance of making the electric current source generating circuit.

Figure 14 is the frequency characteristic of the output current of a kind of Wilson of utilization current mirror current source with high output impedance of making the electric current source generating circuit.

Embodiment

A kind of current source with high output impedance that the present invention proposes, its structured flowchart comprise that an electric current source generating circuit and an equivalent negative resistance produce circuit as shown in Figure 2.Electric current source generating circuit wherein is used to produce a positive resistance and a reference current.This electric current source generating circuit can be realized with all current source circuits.At this is that embodiment illustrates principle of work with wherein cascode current mirroring circuit only:

The electric current source generating circuit is realized with the Cascode current mirror, being comprised:

(1) current reference source Iref1 is used to produce steady current, and one end and external power supply join, and the drain electrode of the other end and NMOS pipe M3 is joined.

(2) four NMOS pipe (M1, M2, M3 and M4) is used to produce the image current of Iref1.NMOS pipe M1 and M2 constitute mirrored transistor, and NMOS pipe M3 and M4 constitute mirrored transistor.The source ground of the nmos pass transistor of two mirror images (M1 and M2) wherein, its grid is connected to each other, and is connected to the drain electrode of NMOS pipe M1, and the source electrode of NMOS pipe M3 is received in the drain electrode of NMOS pipe M1, and the source electrode of NMOS pipe M4 is received in the drain electrode of NMOS pipe M2; The grid of the NMOS pipe (M3 and M4) of two other mirror image interconnects, and is connected to the drain electrode of NMOS pipe M3, and the end of reference source Iref1 is received in the drain electrode of NMOS pipe M3.

Equivalent negative resistance wherein produces circuit and comprises:

(1) PMOS pipe M5, the grid of PMOS pipe M5 and drain electrode short circuit, its drain electrode is connected on the drain electrode of NMOS pipe M6.

(2) NMOS pipe M6 are used for providing bias current to PMOS pipe M5.The grid of NMOS pipe M6 meets biasing voltage signal Vbias1, and its source electrode is connected with ground, and the drain electrode of NMOS pipe M6 is connected with the drain electrode of NMOS pipe M5.

(3) cmos amplifier A1, its voltage gain is slightly larger than 1.The source electrode of the input end of cmos amplifier A1 and PMOS pipe M5 joins, and grid and the drain electrode of the output terminal of cmos amplifier A1 and PMOS pipe M5 are joined.

Wherein, the cmos amplifier A1 in the equivalent negative resistance generation circuit comprises:

The first order of a PMOS pipe M7 and a NMOS pipe M10 formation amplifier is used for that signal is carried out the first order and amplifies; The second level of a PMOS pipe M11 and a NMOS pipe M8 formation amplifier is used for that signal is carried out the second level and amplifies; Two NMOS pipes (M9 and M12) constitute the third level of amplifier; The grid of PMOS pipe M7 is as the input end of cmos amplifier A1, and its source electrode and additional power source join, and its drain electrode is joined with the grid that NMOS manages M8; NMOS manages the grid and drain electrode short circuit of M10, and joins with the drain electrode of PMOS pipe M7, and the source electrode of NMOS pipe M10 is connected with ground; The grid of PMOS pipe M11 and drain electrode short circuit, and join with the drain electrode of NMOS pipe M8 and the grid of NMOS pipe M9 simultaneously; The grid of NMOS pipe M8 joins with the drain electrode of PMOS pipe M7 and the drain electrode of NMOS pipe M10 simultaneously, and the drain electrode of NMOS pipe M8 is joined with the drain electrode of PMOS pipe M11 and the grid of NMOS pipe M9 simultaneously, and the source electrode of NMOS pipe M8 is connected with ground; The source electrode of NMOS pipe M9 is connected with the drain electrode of NMOS pipe M12, and drain electrode and the additional power source of NMOS pipe M9 join; The grid of NMOS pipe M12 meets biasing voltage signal Vbias1, and the source electrode of NMOS pipe M12 joins with ground.

Described electric current source generating circuit with the annexation that equivalent negative resistance produces circuit is: the drain electrode of NMOS pipe M4 links to each other with the source electrode of PMOS pipe M5 and the grid of PMOS pipe M7 simultaneously; The output terminal of whole current source is the drain electrode of NMOS pipe M4, the source electrode of PMOS pipe M5 and the common tie point that PMOS manages the grid of M7.

Above-mentioned embodiment produces the principle of high output impedance:

(1). a kind of current source with high output impedance that the present invention proposes is the positive output impedance R that utilizes the electric current source generating circuit _CmAn equivalent negative resistance in parallel produces the equivalent negative resistance R of circuit _Gain, realize the high output impedance R of whole current source _Out:

$R_{\mathrm{out}}=\frac{R_{\mathrm{cm}}{R}_{\mathrm{gam}}}{R_{\mathrm{cm}}+R_{\mathrm{gam}}}$ (1)

R wherein _CmBe positive resistance, R _GainBe equivalent negative resistance.Described | R _Gain| be slightly larger than | R _Cm|, then can be so that the resistance R of current source _OutHigh.

(2). the cascode current mirror in the above-mentioned electric current source generating circuit as shown in Figure 3, its ac small signal output impedance is determined by following formula:

R _cm≈g _m4·R _ds4·R _ds2 (2)

(3). grid and the drain electrode of PMOS among Fig. 3 pipe M5 link to each other, and the grid of PMOS pipe M5 links to each other with the leakage that NMOS manages M6 with drain electrode, and the grid that NMOS manages M6 is connected on biasing voltage signal contact V _Bias1, its source electrode is connected with ground, and NMOS pipe M6 is used for providing bias current to PMOS pipe M5.The ac small signal equiva lent impedance of PMOS pipe M5 is Rds5.Amplifier A1 shown in Fig. 3 is the cmos amplifier of three grades of amplifications.The first order is the reverse amplifier stage of common source, its voltage gain A _V1≈-g _M7/ g _M10The second level also is the reverse amplifier stage of common source, its voltage gain A _V2≈-g _M8/ g _M11The third level is the forward amplifier stage of common leakage, its voltage gain A _V3≈ g _M9/ (g _M9+ g _Mb9).Therefore the total voltage gain of cmos amplifier A1 is:

$A_V=A_{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="A20051002112200151.png,A20051002112200152.png"\; state="\{\{state\}\}">V</figure-callout>}1}\&CenterDot;A_{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="A20051002112200151.png,A20051002112200152.png"\; state="\{\{state\}\}">V</figure-callout>}2}\&CenterDot;A_{\mathrm{<figure-callout\; id="3"\; label="V"\; filenames="A20051002112200152.png,A20051002112200153.png"\; state="\{\{state\}\}">V</figure-callout>}3}=(-\frac{g_{m7}}{g_{m10}})(-\frac{g_{m8}}{g_{m11}})\left(\frac{g_{m9}}{g_{m9}+g_{\mathrm{mb}9}}\right)=\frac{g_{m7}{g}_{m8}{g}_{m9}}{g_{m10}{g}_{m11}(g_{m9}+g_{\mathrm{mb}9})}$ (3)

As shown in Figure 3, from the common tie point of the grid of the source electrode of PMOS pipe M5 and PMOS pipe M7 see into equivalent resistance be:

$R_{\mathrm{gain}}=\frac{{\mathrm{<figure-callout\; id="5"\; label="R\; ds"\; filenames="A20051002112200153.png,A20051002112200162.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{ds}}}{1-A_V}$ (4)

(4). at the output current I of the current source of high output impedance of the present invention _OutThe equivalent resistance that port is seen is:

$R_{\mathrm{eq}}=R_{\mathrm{out}}=R_{\mathrm{cm}}//R_{\mathrm{gain}}=\frac{R_{\mathrm{cm}}\&CenterDot;R_{\mathrm{gain}}}{R_{\mathrm{cm}}+R_{\mathrm{gain}}}$ (5)

The gain A v that makes COMS amplifier A1 by parameter designing is slightly greater than 1, like this R _GainBe exactly an equivalent negative resistance.Design R _GainAbsolute value be slightly larger than R _CmAbsolute value, so just make R _EqDenominator R _Cm+ R _GainBecoming is slightly less than 0, thereby obtains a very large positive resistance R _Eq, the purpose of the high output impedance of realization current source makes the outputting current steadily performance of current source largely be improved simultaneously.The output impedance R of the single Cascode current mirroring circuit that the present invention is designed _Cm=30.1552M Ω, equivalent negative resistance produces the output impedance R of circuit _Gain=-30.7058M Ω, total output impedance R of the high impedance current source of the present invention's design _Eq=1.6817G Ω.

(5). the output current characteristic curve of the high output impedance current source of making the electric current source generating circuit with the Cascode current mirror of the present invention is as shown in Figure 7.In the comparison according to the Vomin of the output current of the current source of the high output impedance of making the electric current source generating circuit with the Cascode current mirror shown in Figure 9, do not add the Vomin ≈ 2.100V that equivalent negative resistance produces the single Cascode current mirror of circuit compensation; But after adding equivalent negative resistance generation circuit compensation, the Vomin of the high output impedance current source of the present invention's design is reduced to Vomin ≈ 1.465V.

The frequency response characteristic of the output current of the high output impedance current source of making the electric current source generating circuit with the Cascode current mirror of the present invention as shown in figure 11, frequency span is 1.04GHz.

The output current of the high output impedance current source of making the electric current source generating circuit with the Cascode current mirror of the present invention and the relation of temperature, as shown in figure 13.In-40 ℃～145 ℃ temperature ranges, the temperature coefficient of electric current only is 10.6ppm/ ℃, and its temperature characterisitic is fine.

The output current characteristic curve of the high output impedance current source of making the electric current source generating circuit with the Wilson current mirror of the present invention as shown in Figure 8.In the comparison according to the Vomin of the output current of the current source of the high output impedance of making the electric current source generating circuit with the Wilson current mirror shown in Figure 10, do not add the Vomin ≈ 2.105V that equivalent negative resistance produces the single Wilson current mirror of circuit compensation; But after adding equivalent negative resistance generation circuit compensation, the Vomin of the high output impedance current source of the present invention's design is reduced to Vomin ≈ 1.483V.

The frequency response characteristic of the output current of the high output impedance current source of making the electric current source generating circuit with the Wilson current mirror of the present invention as shown in figure 11, frequency span is 1.03GHz.

The output current of the high output impedance current source of making the electric current source generating circuit with the Wilson current mirror of the present invention and the relation of temperature, as shown in figure 14.In-40 ℃～145 ℃ temperature ranges, the temperature coefficient of electric current only is 10.5ppm/ ℃, and its temperature characterisitic is fine.

Claims (10)

1, a kind of current source with high output impedance comprises an electric current source generating circuit, it is characterized in that, it comprises that also an equivalent negative resistance produces circuit, and described equivalent negative resistance produces circuit and the electric current source generating circuit is in parallel.

2, a kind of current source with high output impedance according to claim 1 is characterized in that, the absolute value that described equivalent negative resistance produces the equivalent negative resistance that circuit produced is slightly larger than the positive resistance that the electric current source generating circuit is produced.

3, a kind of current source according to claim 2 with high output impedance, it is characterized in that, described equivalent negative resistance produces circuit and comprises a PMOS pipe (M5), NMOS pipe (M6) and an amplifier, and the voltage gain of described amplifier is slightly larger than 1; Its annexation is: the grid of PMOS pipe (M5) and drain electrode short circuit, and its drain electrode is connected on the drain electrode of NMOS pipe (M6); The grid of NMOS pipe (M6) connects biasing voltage signal (Vbias1), and its source electrode is connected with ground, and the drain electrode of NMOS pipe (M6) is connected with the drain electrode of NMOS pipe (M5); The source electrode of amplifier input terminal Vi and PMOS pipe (M5) joins, and the grid and the drain electrode of the output end vo of amplifier and PMOS pipe (M5) are joined.

4, a kind of current source according to claim 3 with high output impedance, it is characterized in that, described amplifier can be a cmos amplifier, and described cmos amplifier (A1) comprises the first order amplifier that a PMOS pipe (M7) and a NMOS pipe (M10) constitute; The second level amplifier that a PMOS pipe (M11) and a NMOS pipe (M8) constitute; The third level amplifier that two NMOS pipes (M9 and M12) constitute; The grid of PMOS pipe (M7) is as the input end of cmos amplifier (A1), and its source electrode and additional power source join, and its drain electrode is joined with the grid that NMOS manages (M8); NMOS manages the grid and drain electrode short circuit of (M10), and joins with the drain electrode of PMOS pipe (M7), and the source electrode of NMOS pipe (M10) is connected with ground; The grid of PMOS pipe (M11) and drain electrode short circuit, and join with the drain electrode of NMOS pipe (M8) and the grid of NMOS pipe (M9) simultaneously; The grid of NMOS pipe (M8) joins with the drain electrode of PMOS pipe (M7) and the drain electrode of NMOS pipe (M10) simultaneously, and the drain electrode of NMOS pipe (M8) is joined with the drain electrode of PMOS pipe (M11) and the grid of NMOS pipe (M9) simultaneously, and the source electrode of NMOS pipe (M8) is connected with ground; The source electrode of NMOS pipe (M9) is connected with the drain electrode of NMOS pipe (M12), and the drain electrode and the additional power source of NMOS pipe (M9) join; The grid of NMOS pipe (M12) connects biasing voltage signal (Vbias1), and the source electrode of NMOS pipe (M12) joins with ground.

5, a kind of current source according to claim 1 with high output impedance, it is characterized in that, described electric current source generating circuit can be the Cascode current mirror, described Cascode current mirror is by four NMOS pipe (M1, M2, M3 and M4) and a current reference source (Iref1) formation, NMOS pipe (M1) constitutes mirrored transistor with NMOS pipe (M2), and NMOS manages (M3) and constitutes mirrored transistor with NMOS pipe (M4); The source ground of the nmos pass transistor of two mirror images (M1 and M2) wherein, its grid is connected to each other, and be connected to the drain electrode of NMOS pipe (M1), the source electrode of NMOS pipe (M3) is received in the drain electrode of NMOS pipe (M1), and the source electrode of NMOS pipe (M4) is received in the drain electrode of NMOS pipe (M2); The grid of the NMOS pipe (M3 and M4) of two other mirror image interconnects, and is connected to the drain electrode of NMOS pipe (M3), and the drain electrode of NMOS pipe (M3) connects additional power source by current reference source (Iref1).

6, a kind of current source according to claim 1 with high output impedance, it is characterized in that, described electric current source generating circuit can be the Wilson current mirror, described Wilson current mirror is by four NMOS pipe (M1, M2, M3 and M4) and a current reference source (Iref1) formation, NMOS pipe (M1) constitutes mirrored transistor with NMOS pipe (M2), and NMOS manages (M3) and constitutes mirrored transistor with NMOS pipe (M4); The source ground of the nmos pass transistor of two mirror images (M1 and M2) wherein, its grid is connected to each other, and be connected to the drain electrode of NMOS pipe (M2), the source electrode of NMOS pipe (M3) is received in the drain electrode of NMOS pipe (M1), and the source electrode of NMOS pipe (M4) is received in the drain electrode of NMOS pipe (M2); The grid of the NMOS pipe (M3 and M4) of two other mirror image interconnects, and is connected to the drain electrode of NMOS pipe (M3), and the drain electrode of NMOS pipe (M3) connects additional power source by current reference source (Iref1).

7, a kind of current source according to claim 1 with high output impedance, it is characterized in that, described electric current source generating circuit can be the Widlar current source, described Widlar current source is made of two nmos pass transistors (M1, M2) and two resistance (R1, R2), the grid of two NMOS pipes is connected to each other, and be connected to the drain electrode of NMOS pipe (M1), the source ground of NMOS pipe (M1), the drain electrode of NMOS pipe (M1) is connected with external power supply by resistance (R1); The source electrode of NMOS pipe (M2) is connected with ground by resistance (R2).

According to claim 3,4,5 described a kind of current sources, it is characterized in that 8, the drain electrode of NMOS pipe (M4) links to each other with the source electrode of PMOS pipe (M5) and the grid of PMOS pipe (M7) simultaneously with high output impedance; The output terminal of whole current source is the drain electrode of NMOS pipe (M4), the source electrode of PMOS pipe (M5) and the common tie point that PMOS manages the grid of (M7).

According to claim 3,4,6 described a kind of current sources, it is characterized in that 9, the drain electrode of NMOS pipe (M4) links to each other with the source electrode of PMOS pipe (M5) and the grid of PMOS pipe (M7) simultaneously with high output impedance; The output terminal of whole current source is the drain electrode of NMOS pipe (M4), the source electrode of PMOS pipe (M5) and the common tie point that PMOS manages the grid of (M7).

According to claim 3,4,7 described a kind of current sources, it is characterized in that 10, the drain electrode of NMOS pipe (M2) links to each other with the source electrode of PMOS pipe (M5) and the grid of PMOS pipe (M7) simultaneously with high output impedance; The output terminal of whole current source is the drain electrode of NMOS pipe (M2), the source electrode of PMOS pipe (M5) and the common tie point that PMOS manages the grid of (M7).

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