# Corrections Needed - Vol III - Semicond - Chptr 1

#### Clifford bailey

Joined Jul 24, 2005
1

Amplifier gain
Because amplifiers have the ability to increase the magnitude of an input signal, it is useful to be able to rate an amplifier's amplifying ability in terms of an output/input ratio. The technical term for an amplifier's output/input magnitude ratio is gain. As a ratio of equal units (power out / power in, voltage out / voltage in, or current out / current in), gain is naturally a unitless measurement. Mathematically, gain is symbolized by the capital letter "A".

For example, if an amplifier takes in an AC voltage signal measuring 2 volts RMS and outputs an AC voltage of 30 volts RMS, it has an AC voltage gain of 30 divided by 2, or 15:

Correspondingly, if we know the gain of an amplifier and the magnitude of the input signal, we can calculate the magnitude of the output. For example, if an amplifier with an AC current gain of 3.5 is given an AC input signal of 28 mA RMS, the output will be 3.5 times 28 mA, or 98 mA:

[attachmentid=802]

The attached CurrentGain.BMP shows that a relationship exists with Current gain as in voltage gain, but the symbols are messed up.

Voutput should be Ioutput
Vinput should be Iinput

Regards,
Cliff Bailey

#### Dcrunkilton

Joined Jul 31, 2004
422
Originally posted by Clifford bailey@Jul 24 2005, 01:50 PM