summary of Amplifier Basics

summary

● Amplifiers are electronic circuits used to increase the amplitude of an electronic signal.

● The transistor is used primarily as an amplifying device.

● The three transistor amplifier configurations are common base, common collector, and common emitter.

● Common-collector amplifiers are used for impedance matching.

● Common-emitter amplifiers provide phase reversal of the input–output signal.

● All transistor amplifiers require two voltages for proper biasing.

● A single voltage source can provide the necessary forward-bias and reverse-bias voltages using a voltage-divider arrangement.

● A voltage-divider feedback arrangement is the most commonly used biasing arrangement.

R4 ● A transistor amplifier can be biased so that all

or part of the input signal is present at the output.

● Class A amplifiers are biased so that the output current flows throughout the cycle.

● Class AB amplifiers are biased so that the output current flows for less than the full but more than half of the input cycle.

● Class B amplifiers are biased so that the output current flows for only half of the input cycle.

Class C amplifiers are biased so that the output current flows for less than half of the input cycle.

● Coupling methods used to connect one transistor to another include resistance-capacitance coupling, impedance coupling, transformer coupling, and direct coupling.

● Direct-coupled amplifiers are used for high gain at low frequencies or amplification of a DC signal.

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