Large signal amplifier

The early stages of amplifier systems are dealing with small signals. These stages are designed to give good voltage gain. Small signal transistors have a power rating of less than half a watt and power transistors have a power rating of more than half a watt.

The later stages of an amplifier system have much larger collector currents, because the load impedances are much smaller (i.e.: Loudspeaker 1W, 4W, 8W, 16W).

Efficiency is most important when large amounts of signal power are required: