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Amplifiers: Cascading Stages
A very weak signal cannot be sufciently amplied by a single stage amplier, like
those we have dealt with so far—ampliers made only of a single biased transistor
forming a complete network. Single-stage transistor ampliers can be inadequate
for meeting most design requirements for any of the four amplier types (voltage,
current, transresistance, and transconductance). If a microphone produces about
20 mV under normal conditions, you will need a single stage of amplication, but
if it produces only 1 mV, you will need two or more stages of amplication, that is,
a multistage amplier, to provide greater amplic ...