7.1 Introduction

Now that we have examined BJT voltage amplifiers in terms of their gain, input impedance and output impedance, it is time that we extend the small signal analysis to larger signals. Of primary importance will be determination of the maximum output voltage swing, or compliance, along with maximum load power, device dissipation requirements and amplifier efficiency. To assist with this, we introduce the concept of the AC load line. In general, we will not concern ourselves with input impedance, voltage gain or even 𝑟_′𝑒. Indeed, we shall simply consider 𝑟′_𝑒 as a source of distortion. Most power amplifiers are configured as voltage followers so we will focus largely on those.