Voltage, Current and Power Gain


Table of Contents - Glossary - Study Aids
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Discussion of Gain and Amplification

Define voltage, current and power gain. Transformer has no power gain, but can have voltage gain at the expense of current gain. The gain of an amplifier containing one device is always smaller than the maximum gain of that device. RF amplifier Impedance matching no transformers

Logic circuits need both voltage and current gain; voltage gain is required to achieve full regeneration of the logic levels after each logic operation, while the current gain sets an upper limit to the fan-out of the logic gate. In principle one could make up for the lack of current/voltage gain by using a transformer. However, they would be very impractical because of their large size, high loss and limited bandwidth.


Voltage Gain

The maximum obtainable small-signal voltage gain of a transistor is given by ratio of the transconductance to the output conductance. This maximum voltage gain can be obtained by biasing the device with an ideal current source. Any load connected to the output will reduce the available voltage gain.


Current Gain

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Power Gain

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