Principles of Analog Electronics

499

Amplifiers: Cascading Stages

A very weak signal cannot be sufciently amplied by a single stage amplier, like

those we have dealt with so far—ampliers made only of a single biased transistor

forming a complete network. Single-stage transistor ampliers can be inadequate

for meeting most design requirements for any of the four amplier types (voltage,

current, transresistance, and transconductance). If a microphone produces about

20 mV under normal conditions, you will need a single stage of amplication, but

if it produces only 1 mV, you will need two or more stages of amplication, that is,

a multistage amplier, to provide greater amplic ...