SU1385256A1 - Differential amplifier - Google Patents

Abstract

This invention relates to radio engineering and provides an increase in the common-mode input current suppression ratio. Differential amplifier contains seven transistors T I-7, three current sources (IT) 8-10. Equal IT currents of 8.9 are amplified by T 1,2 ,. pass through T 7 and unlock T 5, 6, while the total current T 1,2 is equal to the current IT 10. The difference of the currents coming to the inputs of the differential amplifier is equal to the difference of the currents T 3, 4 and is equal to the difference of the base currents T 1 , 2. Thus, the difference in input currents is amplified by a differential cascade of T 1.2. The differential amplifier has a small input impedance and potential input bias, which allows it to be used as a current amplifier. 1 il.

Description

This invention relates to radio engineering and can be used in integrated semiconductor devices.

The purpose of the invention is to increase the suppression ratio of the in-phase input current.

The drawing shows a circuit diagram of a differential amplifier.

The differential amplifier contains the first 1, second 2, third 3, fourth 4, fifth 5, sixth 6 and seventh 7 transistors, first 8, second 9 and third 10 current sources, first II and second 12 power supply buses. .

Differential amplifier works as follows.

Equal currents of current sources 8 and 9 are amplified by transistors 1 and 2, pass through transistor 7 and unlock transistors 5 and 6 in such a way that currents of transistors 3 and 4 are equal to currents of current sources 8 and 9. In this case, the total current of the transistors I and 2 is equal to the current of the current source 10. The difference of the currents flowing through the inputs of the differential amplifier is equal to the difference of the currents of the transistors 3 and 4 and is equal to the difference of the base currents of the transistors 1 and 2. Thus, the difference of the input currents is amplified P) times the differential cascade at the inputs 1 the midpoint of the power supply is equal to the voltage difference between the emitter-base of transistors 3 and 4 and transistor 7, i.e. does not exceed a few millivolts.

The common-mode input impedance of the amplifier is:

Rsx.C 4 T / | l8.-,

.C "p

where t | - temperature potential

pn junction; Ig, - current sources 8 and 9 current;

| 5 - gain transistors

current.

Differential input resistance is

Rex.a 2cf, / Ig,.

Thus, the proposed differential amplifier has a small input impedance and potential input bias, which makes it possible to use it as a current amplifier.

Claims (1)

Invention Formula Differential amplifier containing the first and second transistors, the collectors of which are the output of the differential amplifier, the bases through the respective first and second current sources are connected to the first power supply bus, the emitters to the bases of the third and fourth transistors, respectively, the collectors of which are connected to the bases of the first and second transistors, and the emitters are the first and second inputs of the differential amplifier, respectively, and connected to the collectors of the fifth and sixth transistors, respectively, the bases of which are combined, the emitters combined and connected to the second power supply bus, which differs. so that, in order to increase the suppression coefficient of the in-phase input current, a third current source and a seventh transistor are introduced, having a structure opposite to the structure of the transistors of the differential amplifier, the collector of which is connected to the bases of the fifth and sixth transistors bus power source, with the emitters of the first and second transistors combined and connected to the emitter of the seventh transistor, the base of which is connected to the common.