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Schematic of an AGC used in the analog telephone network; the feedback from output level to gain is effected via a Vactrol resistive opto-isolator.. Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the input.
A gain greater than one (greater than zero dB), that is, amplification, is the defining property of an active device or circuit, while a passive circuit will have a gain of less than one. [4] The term gain alone is ambiguous, and can refer to the ratio of output to input voltage (voltage gain), current (current gain) or electric power (power ...
Thus a meter with a 50 μA movement will have a "sensitivity" of 20,000 Ω/V. "Per volt" refers to the fact that the impedance the meter presents to the circuit under test will be 20,000 Ω multiplied by the full-scale voltage to which the meter is set. For example, if the meter is set to a range of 300 V full scale, the meter's impedance will ...
If one input of an analog multiplier is held at a steady-state voltage, a signal at the second input will be scaled in proportion to the level on the fixed input. In this case, the analog multiplier may be considered to be a voltage controlled amplifier. Obvious applications would be for electronic volume control and automatic gain control (AGC ...
When testing, they are often difficult to probe as the impedance of an oscilloscope or multimeter can heavily affect the signal or voltage on the node. High impedance signal outputs are characteristic of some transducers (such as crystal pickups); they require a very high impedance load from the amplifier to which they are connected.
In electronics the amplification factor, or gain, is the ratio of the output to the input of an amplifier, sometimes represented by the symbol A F. In numerical analysis the amplification factor is a number derived using Von Neumann stability analysis to determine stability of a numerical scheme for a partial differential equation .
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The use of voltage gain figure is appropriate when the amplifier's input impedance is much higher than the source impedance, and the load impedance higher than the amplifier's output impedance. If two equivalent amplifiers are being compared, the amplifier with higher gain settings would be more sensitive as it would take less input signal to ...