C.3. Amplifier Voltage Gain
Any transistor amplifier stage has a gain from the input terminal to its output terminal (base and collector, respectively, for this case). But the circuit gain, from the source to the output, takes into consideration the possible finite input resistance at the transistor input terminal. Due to the finite signal-source resistance, an attenuation results from the signal-source to the transistor input terminal. The example of this case of the common-emitter amplifier stage is considered here.