It was shown in the previous chapter that the common-base amplifier has a current gain of just less than unity, that its input resistance is low, output resistance high and that it can give substantial voltage gain. In this chapter we shall show how these resistances and the voltage gain depend on the values of re, rb and rc and on the value of the source and load resistance.
A simplified circuit of a transistor common-base amplifier is given in Fig. 3.1(a) in which Rs represents the internal resistance of the signal source and Rl represents the collector load for the amplifier. For the sake of simplicity, methods of applying bias are not indicated.