ABSTRACT
This chapter deals with small-signal design using discrete transistors, specifically bipolar junction transistor. Transistor operation is thus: if the base is open-circuit, then no collector current flows, as the collector-base junction is effectively a reverse-biased diode. A buffer stage is used to isolate two portions of circuitry from each other. It has a high input impedance and low output impedance; typically it prevents things downstream from loading things upstream. The gain of an emitter-follower is always slightly less than unity, because of the finite transconductance of the transistor. Emitter-follower distortion is mainly second harmonic, except when closely approaching clipping. This is entirely predictable, as the circuit is asymmetrical. The emitter-follower is about as simple as an amplifier gets, and it seems highly unlikely that it could suffer from obscure stability problems. The first shortcoming can be addressed by adding a second transistor to increase the negative feedback factor by increasing the open-loop-gain.
