What are the main performance indicators of the differential amplifier?

(3) For differential amplification, due to the symmetry of the circuit, the output drift voltage of the two tubes caused by the temperature change and other factors must be equal in magnitude and the same polarity, that is, the common mode signal.When the input signal is a common mode signal, the collector currents of the two tubes produce equal current increments due to circuit symmetry.Even for a single output circuit, since the common mode Resistors has a large value, a large feedback voltage is generated, and the amplification voltage is low, the common mode signal can be well suppressed, thereby stabilizing the operating point and suppressing zero drift.The stronger the suppression of the common mode amplification, the better the performance of the amplifier.