Digital automatic gain control, as for a receiver

DETAILED DESCRIPTION What is claimed is: 1.
A gain control for a gain-controllable circuit comprising: means for converting an output signal from the gain-controllable circuit into digital data; a first digital comparator comparing a representation of the magnitude value of the digital data to a digital reference value to produce a digital error value; a generator of an output signal responsive to the digital error value; and a low-pass filter responsive to the output signal to apply a gain control signal to said gain-controllable circuit, wherein said generator comprises a pulse width modulator responsive to the digital error value and a second low-pass filter coupled thereto to provide the output signal.
2.
The gain control of claim 1 further comprising a digital absolute value generator and a low-pass filter responsive to said digital data to produce the representation of the magnitude value thereof.
3.
The gain control of claim 1 wherein said means for converting includes an analog-to-digital converter.
4.
The gain control of claim 1 wherein said low-pass filter includes a Miller integrator.
5.
The gain control of claim 1 wherein said gain-controllable circuit includes at least one of a gain-controllable amplifier and a controllable attenuator.
6.
The gain control of claim 5, wherein said gain-controllable amplifier is an IF amplifier as for a television receiver.
7.
A gain control for a gain-controllable circuit comprising: means for converting an output signal from the gain-controllable circuit into digital data; a first digital comparator comparing a representation of the magnitude value of the digital data to a digital reference value to produce a digital error value; a generator of an output signal responsive to the digital error value; and a low-pass filter responsive to the output signal to apply a gain control signal to said gain-controllable circuit, wherein said generator comprises at least one digital value comparator comparing the digital error value to a second digital reference value to produce said output signal