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Simple Transistor Amplifier

<^< Transistor Amplifier Circuits | Course Index | Worksheet: Simple Transistor Amplifier >^>(:nl:)

The signal input (a sine, square, pulse or complex waveform) is 'AC coupled' into the base of the transistor via capacitor, C'_1_'. This removes any direct current component present at the input and also prevents the bias current from flowing back towards the input terminal. Base current is supplied by R'_1_' which is connected to the positive supply rail.

The collector current, I'_C_', flows through the collector load resistor, R'_2_'. The AC component of the collector current results in an AC voltage drop ( equivalent to the change in I'_C_' x R'_2_') which is passed to the output terminal via a second coupling/d.c. blocking capacitor, C'_2_'. The stage gives a voltage gain of about 50 with the following typical values;

* TR'_1_' = BC108, * V'_CC_' = 6V, * R'_1_'= 1M&#937;, * R'_2_'= 1k&#937;, and * C'_1_' = C'_2_' = 10&#956;F.

Note that the output signal is inverted (i.e. 180° out of phase with the input). (:nl:)(:table style="clear:both":)