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In a common-emitter transistor amplifier, the audio output voltage developed across a 2 kΩ collector resistor is 2 V. If the base resistance is 1 kΩ and the transistor current gain is 100, what is the input signal voltage?

0.1 V
1.0 V
1 mV
10 mV

Correct answer: 10 mV

Solution

Voltage gain Av = beta * Rc/Rin = 100 * 2000/1000 = 200. Input signal = Vout/Av = 2/200 = 0.01 V = 10 mV.

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