US 4,380,737 A · Fast AGC slew circuit

Abstract

A fast slew rate automatic gain control circuit (10) includes a variable gain amplifier (14) which is responsive to a gain control signal and an amplitude detector (18) which produces an amplitude signal corresponding to the amplitude of the received signal transmitted through amplifier (14). The amplitude signal is provided to the input node of a loop filter (24) and to the inputs of threshold detectors (30, 32). Positive and negative slew threshold circuits (34, 38) provide threshold signals respectively for the threshold detector circuits (30, 32). When the amplitude signal is within the range of the threshold signals the loop filter produces the gain control as the function of the amplitude signal. When the amplitude signal is less than the positive slew threshold signal the threshold detector (32) produces a drive signal which is provided to the loop filter (24) and causes the generation of the gain control signal to have an accelerated positive slew rate which increases the gain. When the amplitude signal exceeds the negative slew threshold signal the threshold detector (30) produces a drive signal which is supplied to the loop filter (24). When the negative drive signal is supplied to the loop filter the gain control signal is generated with an accelerated negative slew rate which increases the gain. The slew rate of the gain control signal is thus a function of the amplitude of the received signal.

Claims10

Dependent claims

An automatic gain control circuit comprising:

a variable gain amplifier having input thereto a received signal and having the gain thereof responsive to a gain control signal;
an amplitude detector connected to receive from said amplifier the received signal transmitted therethrough, said amplitude detector generating an amplitude signal corresponding to the amplitude of the received signal input to said amplitude detector;
means for generating a first drive signal when said amplitude signal exceeds a first threshold signal;
means for generating a second drive signal when said amplitude signal is less than a second threshold signal;
and
means for generating a first gain control signal varying as a function of said amplitude signal when said amplitude signal is between the amplitudes of said threshold signals, generating a second gain control signal varying as a function of said first drive signal when said amplitude signal exceeds the amplitude of said first threshold signal and generating a third gain control signal varying as a function of said second drive signal when said amplitude signal is less than the amplitude of said second threshold signal.

3 more elements

An automatic gain control circuit comprising;

a variable gain amplifier having input thereto a received signal and having the gain thereof varying in accordance with a gain control signal;
an amplitude detector connected to receive from said amplifier the received signal transmitted therethrough, said amplitude detector generating an amplitude signal corresponding to the amplitude of the received signal input to the amplitude detector;
a first comparator having said amplitude signal as a first input and a first threshold signal as a second input and generating a first switch control signal when said amplitude signal exceeds said first threshold signal;
a second comparator having said amplitude signal as a first input and a second threshold signal as a second input and generating a second switch control signal when said amplitude signal is less than said second threshold signal;
a loop filter having an input terminal for receiving said amplitude signal, said loop filter generating said gain control signal;
a first switch for connecting a first drive signal to a second input terminal of said loop filter upon receipt of said first switch control signal;
and
a second switch for connecting a second drive signal to the third terminal of the loop filter upon receipt of the second switch control signal;
said loop filter generating a gain control signal varying as a function of the amplitude signal when the amplitude signal is between the amplitude of the threshold signals, and generating a gain control signal that varies as a function of the first drive signal when the amplitude signal exceeds the amplitude of the first threshold signal and generates a gain control signal that varies as a function of a second drive signal when the amplitude signal is less than the amplitude of the second threshold signal.

6 more elements

Dependencies are inferred from the claim text.

Fast AGC slew circuit

Life of this patent

Fast AGC slew circuit

Life of this patent

Abstract

Claims10