Comparison of Saturated and Nonsaturated Switching Circuit Techniques

The concept that the junction transistor is a charge-controlled current source is reviewed. Saturated operation and non-saturated operation are defined on the basis of minority and majority carrier distributions in the base region. Several common emitter switching circuits are analyzed. The switching efficiency, a figure of merit based on the charge storage properties of the transistor, is introduced. Saturated and nonsaturated operation are compared on the basis of switching efficiency, transient waveforms, stability of the voltage levels, power dissipation, noise rejection and suppression ablity, and circuit complexity. Currently-used antisaturation techniques are discussed.