Fast response dynamic gain control circuit

Claim 2

A fast response dynamic gain control circuit for an audio frequency amplification system comprising operational audio amplifier means having a first signal input, a second signal input, a predetermined maximum output level and an output said first signal input being adapted for coupling to an audio frequency signal which is amplified by said amplifier means and coupled to said output, said second signal input being responsive to an applied feedback signal for varying the amplification of said amplifier means, and control means responsive to said amplified audio signal exceeding a predetermined threshold level for varying said feedback signal to adjust said amplification in proportion to the amount said amplified audio signal exceeds said threshold level, said control means including threshold level sensing means coupled to said output for providing said threshold level at a level slightly below said maximum output level and for producing a control voltage proportional to the amount said amplified audio signal exceeds such threshold level, said control means also including insulated gate field effect transistor means having a gate input coupled to said threshold level sensing means and an output terminal coupled to said second signal input for varying said feedback signal in response to variations in said control voltage said gain control circuit also including variable resistor means coupled between said output and said second input of said operational amplifier means for producing said feedback signal for varying the gain of said amplifier, said field effect transistor means serving as a voLtage variable impedance to also vary said feedback signal.

Claim 3

A fast response dynamic gain control circuit as in claim 1 where said second signal input is an inverting type input.

Claim 4

A fast response dynamic gain control circuit for an audio frequency amplification system comprising operational audio amplifier means having a first signal input, a second signal input, a predetermined maximum output level and an output said first signal input being adapted for coupling to an audio frequency signal which is amplified by said amplifier means and coupled to said output, said second signal input being responsive to an applied feedback signal for varying the amplification of said amplifier means, and control means responsive to said amplified audio signal exceeding a predetermined threshold level for varying said feedback signal to adjust said amplification in proportion to the amount said amplified audio signal exceeds said threshold level, said control means including threshold level sensing means coupled to said output for providing said threshold level at a level slightly below said maximum output level and for producing a control voltage proportional to the amount said amplified audio signal exceeds said threshold level said threshold level sensing means including a level sensing network coupled to said output and integration means coupled to said level sensing network said integration means providing said control voltage and transistor amplifier means coupling said level sensing network to said integration means, said transistor means being in a conductive condition in response to said amplified audio signal exceeding said threshold level, said control means also including insulated gate field effect transistor means having a gate input coupled to said threshold level sensing means and an output terminal coupled to said second signal input for varying said feedback signal in response to variations in said control voltage.

Claim 5

A fast response dynamic gain control circuit for an audio frequency amplification system comprising operational audio amplifier means having a first signal input, a second signal input, a predetermined maximum output level and an output said first signal input being adapted for coupling to an audio frequency signal which is amplified by said amplifier means and coupled to said output, said second signal input being responsive to an applied feedback signal for varying the amplification of said amplifier means, and control means responsive to said amplified audio signal exceeding a predetermined threshold level for varying said feedback signal to adjust said amplification in proportion to the amount said amplified audio signal exceeds said threshold level, said control means including threshold level sensing means coupled to said output for providing said threshold level at a level slightly below said maximum output level and for producing a control voltage proportional to the amount said amplified audio signal exceeds said threshold level said threshold level sensing means including a level sensing network coupled to said output and integration means coupled to said level sensing network said integration means providing said control voltage and transistor amplifier means coupling said level sensing network to said integration means, said transistor means being in a conductive condition in response to said amplified audio signal exceeding said threshold level, said control means also including insulated gate field effect transistor means having a gate input coupled to said threshold level sensing means and an output terminal coupled to said second signal input for varying said feedback signal in response to variations in said control voltage.

Claim 6

A fast response dynamic gain control circuit as in claim 3 in which said integration means includes a capacitor, series connected resistor and a voltage source coupled across said capacitor and resistor for charging said capacitor, said transistor means being coupled across said capacitor said conduction of said transistor means discharging said capacitor in proportion to the average of the amount said amplified audio signal exceeds said threshold level.