For a common emitter-transistor, amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V. Suppose the current amplification factor of the transistor is 100, find the input signal voltage and base current, if the base resistance is 1 kΩ.

Solution

Given, a common-emitter transistor configuration.

$Collector resistance, R_{c} = 2000 Ω Output voltage, V_{0} = 2 V Current amplification factor, β_{ac} = 100 Input voltage, V_{i} = ? Current across base, I_{b} = ? Input resistance, R_{i} = 1000 Ω$

As, voltage gain, $A_{v} = \frac{V_{0}}{V_{i}} = β_{ac} \frac{R_{0}}{R_{i}}$

$\Rightarrow$ Input signal voltage, $V_{i} = \frac{V_{0}}{β_{ac} . (R_{0} / R_{i})}$

$= \frac{2}{100 (2000 / 1000)} = 0.01 V$

Base current, $I_{b} = \frac{V_{i}}{R_{i}} = \frac{0.01 V}{1000 Ω} = 10 μA$ .

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Wave Optics

For a common emitter-transistor, amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V. Suppose the current amplification factor of the transistor is 100, find the input signal voltage and base current, if the base resistance is 1 kΩ.

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