Voltage, Current and Power Gain
Table of Contents -
In this Section
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.
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.
The maximum obtainable small-signal voltage gain of a transistor
is given by ratio of the transconductance to the
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.