RU2101851C1 - Differential amplifier - Google Patents

Abstract

FIELD: radio engineering, applicable in radio electronic device of various purpose, in particular, in amplifying devices, pulsers, self-excited oscillators. SUBSTANCE: differential amplifier uses transistors 1,2,3,4, current generator 5. Transistors 3,4 are double-emitter ones and current generators 6,7,8 are introduced. By varying the currents of the current generators it becomes possible to obtain both a wall-defined transmission characteristic with a controllable mutual conductance and a characteristic with a controllable hysteresis. EFFECT: expanded functional abilities of differential amplifier due to electronic control of the nonlinearity mode of its transmission characteristic. 3 wdg

Description

 The invention relates to radio engineering and can be used in electronic devices for various purposes, in particular, in amplifying devices, pulse devices, oscillators.

 Known differential amplifier (International patent N 83/03612, CL H 03 F 1/32, 3/45), containing the first and second transistors, the bases of which are the corresponding inputs, and the collector outputs of the amplifier, the emitters are connected directly to the collectors of the third and fourth transistors and through voltage repeaters with bases of the fourth and third transistors, respectively, between the emitters of the third and fourth transistors, a resistor is included.

 The disadvantage of this differential amplifier is the inability to electronically control the steepness of the transfer characteristic.

 Also known differential amplifier according to the Application of Japan N 61-47007, CL. H 03 F 3/50, 3/343, containing the first and second transistors, the bases and collectors of which are the corresponding inputs and outputs of the differential amplifier, the emitters are connected respectively to the collectors of the third and fourth transistors, the emitters of which are connected by the output of the current generator, the base of the third transistor is connected with the emitter of the second transistor, the base of the fourth transistor is connected to the emitter of the first transistor.

 The disadvantage of this amplifier is a strong change in its dynamic range with electronic control of the steepness of the transfer characteristic, as well as the inability to control the type of non-linearity of the transfer characteristic.

 The closest in technical essence to the claimed object is a differential amplifier (Japanese Application N 4-14802, CL H 03 F 3/45, H 03 K 19/086), containing the first and second transistors, the bases of which are the corresponding inputs of the differential amplifier, the emitter of the first transistor is connected to the collectors of the third transistor and the base of the fourth transistor, the emitter of the second is connected to the collector of the fourth transistor and the base of the third transistor, the emitters of the third and fourth transistors with the output of the first current generator.

 The disadvantage of this differential amplifier is the inability to electronically control the type of nonlinearity of its transfer characteristic, which limits its functionality.

 The purpose of the invention is the expansion of the functionality of a differential amplifier by providing electronic control of the type of nonlinearity of its transfer characteristic.

 The goal is achieved in that in a differential amplifier containing the first and second transistors, the bases of which are the corresponding inputs of the differential amplifier, the emitter of the first transistor is connected to the collector of the third transistor and the base of the fourth transistor, the emitter of the second transistor is connected to the collector of the fourth transistor and the base of the third transistor, emitters of the third and fourth transistors are connected to the output of the first current generator, the third and fourth transistors are made two emitte GOVERNMENTAL, wherein the second emitters of these transistors are connected to the generator output inputted second current collectors of the third and fourth transistors are connected to the outputs of the respective input of the third and fourth current generators, collectors of the first and second transistors are the respective outputs of the differential amplifier.

 The inventive differential amplifier is illustrated in FIG. 1, which shows its electrical circuit diagram, in FIG. 2 shows the distribution of currents in an amplifier during its operation; FIG. 4 shows the transfer characteristic of a differential amplifier.

 The differential amplifier contains the first 1, second 2, third 3, fourth 4 transistors, the first 5, second 6, third 7 and fourth 8 current generators.

 We consider the operation of a differential amplifier under the following assumptions: all transistors are identical (except for the areas of the first and second emitters of transistors 3 and 4 being different), the base currents of transistors are negligible compared to their collector currents, transistors operate at frequencies much lower than the cutoff frequency of their transfer coefficient current in the circuit with a common base.

где I₀₃₁, I₀₃₂, I₀₄₁, I₀₄₂ токи покоя, протекающие в соответствующих эмиттерах транзисторов 3 и 4, S_э31, S_э32, S_э41, S_э42 площади соответствующих эмиттерных р-н-переходов транзисторов 3 и 4.Initially, supply voltages, bias voltage are supplied to the amplifier inputs and currents of current generators of such a magnitude as to bring all transistors into active mode. In this case, the emitter currents of transistors 1 and 2 are set equal to I ₀₂ -I ₀₁ , where I _{02 the} current of generators 5 and 6, I _{01 the} current of current generators 7 and 8, and the values of the emitter currents of transistors 3 and 4 are determined by the following expressions:

where I ₀₃₁ , I ₀₃₂ , I ₀₄₁ , I ₀₄₂ quiescent currents flowing in the respective emitters of transistors 3 and 4, S _e31 , S _e32 , S _e41 , S _{e42 are the} areas of the corresponding emitter rn junctions of transistors 3 and 4.

При подаче на входы усилителя дифференциального входного напряжения U_вх в цепях транзисторов 1 и 2 протекает дифференциальный выходной ток i_вых, равный сумме токов i₁ и i₂, протекающих в цепях соответственно первых и вторых эмиттеров транзисторов 3 и 4:
i_вых i₁+i₂ (3)
Входное напряжение равно:
U_вх U_бэ1 + U_бэ41 U_бэ31 U_бэ2 U_бэ1 + U_бэ42 U_бэ32 U_бэ2, (4)
где U_бэ1, U_бэ2 базо-эмиттерные напряжения транзисторов 1 и 2, соответственно;
U_бэ31, U_бэ32, U_бэ41, U_бэ42 базо-эмиттерные напряжения в цепях соответственно первых и вторых эмиттеров транзисторов 3 и 4.We restrict ourselves to considering the symmetric structure of the amplifier when S _e31 S _e42 S ₁ , S _e32 S _e41 S ₂ . Wherein

When applying to the inputs of the amplifier a differential input voltage U _I in the circuits of transistors 1 and 2, a differential output current i _o flows equal to the sum of the currents i ₁ and i ₂ flowing in the circuits of the first and second emitters of transistors 3 and 4, respectively:
i _out i ₁ + i ₂ (3)
Input voltage is:
U _I U U _BE1 + U _BE41 U _BE31 U _BE2 U _BE1 + U _BE42 U _BE32 U _BE2 , (4)
where U _be1 , U _{be2 are the} base-emitter voltages of transistors 1 and 2, respectively;
U _BE31 , U _BE32 , U _BE41 , U _{BE42 are the} base-emitter voltages in the circuits of the first and second emitters of transistors 3 and 4, respectively.

Из (5) видно, что

Совместное решение уравнений (6) и (3) с учетом (2) позволяет выразить i₁ и i₂ через i_вых:

Подставив (7) в (5), после преобразования получим следующее уравнение передаточной характеристики дифференциального усилителя:

Электронное управление видом нелинейности передаточной характеристики осуществляется путем изменения соотношения токов I₀₁ и I₀₂ - фиг. 3. Анализ уравнения (8) показывает, что при

передаточная характеристика дифференциального усилителя является однозначной, если же

то она имеет гистерезис. В первом случае изменением отношения

можно регулировать крутизну передаточной характеристики, во втором величину гистерезиса.Representing the values of the base-emitter voltages using the Ebers-Moll equation up to the value of the reverse current of the rn junction, we transform (4) to the following form:

From (5) it can be seen that

The joint solution of equations (6) and (3) with allowance for (2) allows us to express i ₁ and i _{2 in} terms of i _out :

Substituting (7) into (5), after conversion, we obtain the following equation of the transfer characteristic of the differential amplifier:

Electronic control of the type of non-linearity of the transfer characteristic is carried out by changing the ratio of currents I ₀₁ and I ₀₂ - FIG. 3. An analysis of equation (8) shows that for

the transfer characteristic of the differential amplifier is unambiguous, if

then it has hysteresis. In the first case, a change in attitude

you can adjust the slope of the transfer characteristic, in the second value of the hysteresis.

 Thus, the proposed differential amplifier compares favorably with the prototype and analogues in that it is possible to electronically modify the form of non-linearity of the transfer characteristic in the range from a single-valued characteristic with adjustable slope to a characteristic with adjustable hysteresis.

Claims (1)

 A differential amplifier containing the first and second transistors, the bases of which are the corresponding inputs of the differential amplifier, the emitter of the first transistor is connected to the collector of the third transistor and the base of the fourth transistor, the emitter of the second transistor is connected to the collector of the fourth transistor and the base of the third transistor, emitters of the third and fourth transistors are connected to the output of the first current generator, characterized in that the third and fourth transistors are made of two-emitter, and the second the emitters of these transistors are connected to the generator output inputted second current collectors of the third and fourth transistors are connected to the outputs of the respective input of the third and fourth current generators, collectors of the first and second transistors are the respective outputs of the differential amplifier.

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