Emitter coupled differential amplifier circuit

Emitter coupled differential amplifier circuit

 (1) Emitter coupling differential amplifier circuit
    In the basic differential amplifier circuit, the symmetry of the circuit is relied upon to suppress zero point drift. The better the symmetry, the better the effect of suppressing zero point drift
. However, in fact, it is impossible for the circuit to be completely symmetrical, so the zero-point drift suppression of the basic differential amplifier circuit is greatly limited. The way to improve it is to connect a resistor
to the emitter of the basic amplifier circuit , as shown in the figure. The reason why the two bias resistors Rb12 and Rb22 can be eliminated is because of the use of dual DC power supplies. Its working principle is briefly described below.