CN204465471U - A kind of adjustable differential amplifier circuit - Google Patents

Abstract

The utility model discloses a kind of adjustable differential amplifier circuit, this circuit is made up of basic amplifier circuit, switch and adjustable electronic element, can be according to demand, by starting, the relevant adjustable device of adjustment, forms different circuit, to in these circuit calibration procedures, theory well in conjunction with reality, can reach the object of proof theory knowledge, and to pinpointing the problems, ask a question, final problem-solving ability has good booster action.

Description

A kind of adjustable differential amplifier circuit

Technical field

The utility model relates to differential amplifier and transistor constant-current source circuit, particularly a kind of adjustable differential amplifier circuit.

Background technology

In the Basic Analog Electronics course of most of colleges and universities, adopt theoretical and test the mode of separating teaching, the circuit of experiment is single, the component values used also is fixing non-adjustable, circuit numerical value change causes direct current biasing in circuit (static state) problem less and exchanges transmission (dynamically) problem and often obscure, in the process of experiment, because circuit is non-adjustable, test data is fixed, often directly quote the test data on book, lack the design of the circuit such as differential amplifier and the process of measurement, the mentality of designing of student can not be inspired, theory can not combine with practice, manipulative ability can not get improving.

Utility model content

The purpose of this utility model is the situation for prior art, and provide a kind of adjustable differential amplifier circuit, this circuit can provide circuit conversion, and conversion is convenient, and adjustable extent is large, and element is less, and transfer admittance is high.

The technical scheme realizing the utility model object is:

A kind of adjustable differential amplifier circuit, comprise the first-six transistor, first control switch connects DC power cathode and first crystal triode, second control switch connects ground and load adjustable resistance, 3rd control switch connects the first collector electrode adjustable resistance and first crystal triode, 6th control switch connects the first base stage adjustable resistance and the first alternating message source or ground connection, first crystal transistor emitter is made to connect ground, base stage connects the first base stage adjustable resistance and connects the first alternating message source or ground connection, emitter connects the first collector electrode adjustable resistance and connects the first controllable impedance again and then connect DC power anode, composition triode amplifier circuit,

Second control switch connects the second transistor and load adjustable resistance, 7th control switch connects the second base stage adjustable resistance and the second alternating message source or ground connection, the collector electrode of first crystal triode is made to connect the collector electrode of the second transistor by load adjustable resistance, the emitter of first crystal triode connects the emitter pole of the second transistor by balance adjustable resistance, form typical long tail type differential amplifier circuit;

First control switch connects balance adjustable resistance and first crystal triode, second control switch connects the second transistor and load adjustable resistance, 4th control switch connects the second collector electrode adjustable resistance and the second transistor, 5th control switch connects the 4th transistor and balance adjustable resistance, 3rd transistor and the 4th transistor and the first adjustable resistance, second adjustable resistance, 3rd adjustable resistance composition constant-current source circuit is as constant-current source bias circuit, balance adjustable resistance is connected to by the 5th control switch, composition constant-current source bias differential amplifier circuit,

First control switch connects balance adjustable resistance and first crystal triode, second control switch ground connection and load adjustable resistance, 3rd control switch connects the 5th transistor and first crystal triode, 4th control switch connects the 6th transistor and the second transistor, 5th control switch connects the 4th transistor and balance adjustable resistance, 6th control switch connects the first base stage adjustable resistance and the first alternating message source or ground connection, 7th control switch connects the second base stage adjustable resistance and the second alternating message source or ground connection, 5th transistor and the 6th transistor form active pull-up circuit, first crystal triode and the second transistor is connected to by the 3rd control switch and the 4th control switch, composition active load differential amplifier circuit.

Also be provided with low-pass filter circuit to be connected with power supply.

The beneficial effects of the utility model are:

The utility model provides a kind of adjustable differential amplifier circuit, this circuit can be according to demand, by starting to adjust relevant adjustable device, form triode amplifier, typical long tail type differential amplifier, constant-current source bias differential amplifier, active load differential amplifier circuit, four kinds of different circuit, to in these circuit calibration procedures, theory can well in conjunction with reality, reach the object of proof theory knowledge, to pinpointing the problems, ask a question, final problem-solving ability has good booster action.This circuit can provide circuit conversion, and conversion is convenient, and adjustable extent is large, and element is less, and transfer admittance is high.

Accompanying drawing explanation

Fig. 1 is the circuit theory diagrams of embodiment;

Fig. 2 is triode amplifier circuit theory diagrams in Fig. 1;

Fig. 3 is typical long tail type differential amplifier circuit schematic diagram in Fig. 1;

Fig. 4 is the reduced graph of Fig. 3;

Fig. 5 is constant-current source bias differential amplifier circuit schematic diagram in Fig. 1;

Fig. 6 is the reduced graph of Fig. 5;

Fig. 7 is active load differential amplifier circuit schematic diagram in Fig. 1;

Fig. 8 is the reduced graph of Fig. 7.

In figure, U1 is the first alternating message source, U2 is the first alternating message source, VCC is DC power anode, VEE is DC power cathode, T1 is first crystal triode, T2 is the second transistor, T3 is the 3rd transistor, T4 is the 4th transistor, T5 is the 5th transistor, T6 is the 6th transistor, T7 is the 7th transistor, R1 is the first adjustable resistance, R2 is the second adjustable resistance, R3 is the 3rd adjustable resistance, Rc1 is the first collector electrode adjustable resistance, Rc2 is the second collector electrode adjustable resistance, Rb1 is the first base stage adjustable resistance, Rb2 is the second base stage adjustable resistance, RL is load adjustable resistance, Rw is balance adjustable resistance, Rem long-tail adjustable resistance, C1 is the first tunable capacitor, C2 is the second tunable capacitor, L1 is the first controllable impedance, L2 is the second controllable impedance, S1 is the first control switch, S2 is the second control switch, S3 is the 3rd control switch, S4 is the 4th control switch, S5 is the 5th control switch, S6 is the 6th control switch, S7 is the 7th control switch.

Embodiment

Below in conjunction with drawings and Examples, the utility model content is described in further detail, but is not to restriction of the present utility model.

Embodiment:

As shown in Figure 1, a kind of adjustable differential amplifier circuit, comprise first crystal triode T1-the 6th transistor T6, first control switch S1 connects DC power cathode VEE and first crystal triode T1, second control switch S2 connects ground and load adjustable resistance RL, 3rd control switch S3 connects the first collector electrode adjustable resistance Rc1 and first crystal triode T1, 6th control switch S6 connects the first base stage adjustable resistance Rb1 and the first alternating message source U1 or ground connection, first crystal triode T1 emitter is made to connect ground, base stage connects the first base stage adjustable resistance Rb1 and connects the first alternating message source U1 or ground connection, emitter meets the first collector electrode adjustable resistance Rc1 and connects the first controllable impedance L1 again and then connect DC power anode VCC, composition triode amplifier circuit,

Second control switch S2 connects the second transistor T2 and load adjustable resistance RL, 7th control switch S7 connects the second base stage adjustable resistance Rb2 and the second alternating message source U2 or ground connection, the collector electrode of first crystal triode T1 is made to connect the collector electrode of the second transistor T2 by load adjustable resistance RL, the emitter of first crystal triode T1 connects the emitter pole of the second transistor T2 by balancing adjustable resistance RW, form typical long tail type differential amplifier circuit;

First control switch S1 connects balance adjustable resistance RW and first crystal triode T1, second control switch S2 meets the second transistor T2 and load adjustable resistance RL, 4th control switch S4 connects the second collector electrode adjustable resistance Rc2 and the second transistor T2, 5th control switch S5 connects the 4th transistor T4 and balance adjustable resistance RW, 3rd transistor T3 and the 4th transistor T4 and the first adjustable resistance R1, second adjustable resistance R2, 3rd adjustable resistance R3 composition constant-current source circuit is as constant-current source bias circuit, balance adjustable resistance RW is connected to by the 5th control switch S5, composition constant-current source bias differential amplifier circuit,

First control switch T1 connects balance adjustable resistance RW and first crystal triode T1, second control switch S2 ground connection and load adjustable resistance RL, 3rd control switch S3 connects the 5th transistor T5 and first crystal triode T1, 4th control switch S4 connects the 6th transistor T6 and the second transistor T2, 5th control switch S5 connects the 4th transistor T4 and balance adjustable resistance RW, 6th control switch S6 connects the first base stage adjustable resistance Rb1 and the first alternating message source U1 or ground connection, 7th control switch S7 connects the second base stage adjustable resistance Rb2 and the second alternating message source U2 or ground connection, 5th transistor T5 and the 6th transistor T6 forms active pull-up circuit, first crystal triode T1 and the second transistor T2 is connected to by the 3rd control switch S3 and the 4th control switch S4, composition active load differential amplifier circuit.

As shown in Figure 2, being triode grounded emitter amplifier circuit part, as U2=0, quiescent point Q point can being measured, by changing the second base stage adjustable electric Rb2 and the second collector electrode adjustable resistance Rc2, coming computation and measurement Q point moves or moves down.When triode normally works (emitter junction positively biased, collector junction is reverse-biased), from U2 input AC small-signal, the dynamic characteristic of triode can be measured.

As shown in Figure 3, Figure 4, for typical long tail type differential amplifier circuit part, 5th control switch S5 meets emitter degeneration biasing resistor (long-tail resistance) Rem, 3rd control switch S3 and the 4th control switch S4 meets the first collector resistance Rc1 and the second collector resistance Rc2 respectively, first control switch S1 meets balance resistance Rw, can obtain typical long tail type differential amplifier circuit figure.Whether the second control switch S2 controls is Single-end output, balance adjustable resistance Rw regulates the symmetry problem of triode, by theory analysis and experiment, long-tail resistance Rem has very strong negative feedback at static (U1=U2=0) to operating current ie1 and ie2, can static working current iee be stablized, suppress working point vary with temperature and produce drift (being commonly referred to null offset) slowly.In multistage direct coupled amplifier, the output interference that null offset produces will make amplifier cannot amplify and export small-signal.The drift of input stage is the main cause producing this interference.If input stage adopts differential amplifier, then will greatly reduce the null offset of direct coupled amplifier.

As shown in Figure 5, Figure 6, for constant-current source bias differential amplifier circuit part, 5th control switch S5 receives ratio constant-current source, 3rd control switch S3 and the 4th control switch S4 meets the first collector resistance Rc1 and the second collector resistance Rc2 respectively, can obtain the differential amplifier circuit figure of constant-current source bias.General Rem is larger, circuit performance is better, in order to improve the temperature stability of circuit, reduce null offset, overcome the impact of two pipe parameter unbalances, and improve circuit to the rejection ability of common-mode signal, all require to choose larger long-tail resistance Rem, adopt constant-current source as the biasing circuit of differential amplifier emitter, constant-current source can provide stable bias current iee for differential amplifier circuit, and constant-current source have very large dynamic internal resistance be used for replace Rem, greatly can improve the rejection ability of differential amplifier to common-mode signal.Current transmission characteristic and the dynamical output resistance of ratio constant-current source are as follows: $\mathrm{iee}\≈\frac{R2}{R1}*\frac{\mathrm{VEE}-U_{\mathrm{BE}3}}{R3+R2};\mathrm{Rem}\≈(1+\frac{{\mathrm{\β}}_4{R}_1}{R_3//R_2+r_{\mathrm{be}4}+R_1})r_{\mathrm{ce}4},$ Obviously this dynamic electric resistor is very large, we can manually regulate the first adjustable resistance R1, the second adjustable resistance R2, the 3rd adjustable resistance R3 to adjust constant-current source bias, 3rd adjustable resistance R3 is 0.8-1.5k Ω, and then has had darker understanding to the difference mode gain of differential amplifier circuit and common-mode rejection properties.

As shown in Figure 7, Figure 8, for active load differential amplifier circuit part, 5th control switch S5 receives ratio constant-current source, and the 3rd control switch S3 and the 4th control switch S4 meets the 5th transistor T5 and the 6th transistor T6 respectively, can obtain active load differential amplifier circuit figure.Second control switch S2 is received ground, form Single-end output.First crystal triode T1 and the second transistor T2 is that cascode differential amplifier is to pipe, 5th transistor T5 and the 6th transistor T6 is positive-negative-positive mirror-image constant flow source, as the differential collector electrode active load to pipe of first crystal triode T1 and the second transistor T2.When input signal is difference mode signal U1=-U2=Uid/2; Ic1=-ic2; Ic3=ic4=ic2; Io1=ic4-ic1=ic4+ic2=2ic2; Io1=ic3-ic2=0; Export earth-current quite with traditional double-width grinding both-end, so achieve when not losing gain, both-end exports the characteristic converting Single-end output to.Constant-current source greatly reduces power consumption as the constant-current source differential amplifier of load, and accomplishes that volume is little, and circuit temperature improves.But with constant-current source as load, in Fig. 8, the output current of first crystal triode T1 pipe is very low, so output voltage U01 is very little, U02 is very large, and the output that result in two pipes is uneven, and this is the place that will note.

Claims (3)

1. an adjustable differential amplifier circuit, it is characterized in that, comprise the first-six transistor, first control switch connects DC power cathode and first crystal triode, second control switch connects ground and load adjustable resistance, 3rd control switch connects the first collector electrode adjustable resistance and first crystal triode, 6th control switch connects the first base stage adjustable resistance and the first alternating message source or ground connection, first crystal transistor emitter is made to connect ground, base stage connects the first base stage adjustable resistance and connects the first alternating message source or ground connection, emitter connects the first collector electrode adjustable resistance and connects the first controllable impedance again and then connect DC power anode, composition triode amplifier circuit,

7th control switch connects the second base stage adjustable resistance and the second alternating message source or ground connection, the collector electrode of first crystal triode is made to connect the collector electrode of the second transistor by load adjustable resistance, the emitter of first crystal triode connects the emitter pole of the second transistor by balance adjustable resistance, form typical long tail type differential amplifier circuit;

First control switch connects balance adjustable resistance and first crystal triode, second control switch connects the second transistor and load adjustable resistance, 4th control switch connects the second collector electrode adjustable resistance and the second transistor, 5th control switch connects the 4th transistor and balance adjustable resistance, 3rd transistor and the 4th transistor and the first adjustable resistance, second adjustable resistance, 3rd adjustable resistance composition constant-current source circuit is as constant-current source bias circuit, balance adjustable resistance is connected to by the 5th control switch, composition constant-current source bias differential amplifier circuit,

First control switch connects balance adjustable resistance and first crystal triode; second control switch ground connection and load adjustable resistance, the 3rd control switch connects the 5th transistor and is connected the 6th transistor with first crystal triode, the 4th control switch and is connected the 4th transistor with the second transistor, the 5th control switch and balances that adjustable resistance, the 6th control switch are connected the first base stage adjustable resistance and the first alternating message source or ground connection, the 7th control switch is connected the second base stage adjustable resistance and the second alternating message source or ground connection; 5th transistor and the 6th transistor form active pull-up circuit, are connected to first crystal triode and the second transistor by the 3rd control switch and the 4th control switch, composition active load differential amplifier circuit.

2. adjustable differential amplifier circuit according to claim 1, is characterized in that, is provided with low-pass filter circuit and is connected with power supply.

3. adjustable differential amplifier circuit according to claim 1, is characterized in that, the 3rd described adjustable resistance is 0.8-1.5k Ω.