The design and calculation of the basic logical circuits
F. Dokter, J. Steinhauer · 1973
By switching operation we understand the situation when the transistor is operated only in two different states. Although switching operation is possible in any of the three basic configurations (common base, common collector and common emitter), the common emitter configuration is generally preferred, since this gives both current amplification and voltage amplification. A transistor can be used either as a voltage switch or as a current switch. In the first case, the voltage across the transistor can assume only two different values, depending on the switching state (see Fig. 5.1).