Two common-emitter transistor amplifiers connected to form a directly coupled two-stage amplifier

Two common-emitter transistor amplifiers connected to form a directly coupled two-stage amplifier

Shown is a direct-coupled two-stage amplifier consisting of two common-emitter (e) transistor amplifiers connected. There is no coupling capacitor in the circuit, and the DC voltage output by the front-stage common-emitter (e) transistor amplifier is directly used as the input voltage of the subsequent-stage common-emitter (e) transistor amplifier. Compared with capacitor-coupled multi-stage amplifiers, direct-coupled multi-stage amplifiers have better low-frequency response. However, when a small change in the power supply occurs, it will also be amplified by the circuit, causing obvious deviation of the circuit. The operating points of two-pole amplifiers influence each other.