Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
255 words
A voltage-controlled variable-gain amplifier system comprising, in combination, an amplifier stage including a first transistor having a base, an emitter and a collector, means to apply an input signal to the base of said first transistor relative to ground, a first resistor connected between the emitter of said first transistor and ground, A second resistor connected between the collector of said first transistor and a source of direct current potential, a control transistor having a base, an emitter and a collector, a third resistor connected between the emitter of said control transistor and ground, a fourth resistor having a resistance substantially equal to the resistance of said third resistor connected between the collector of said control transistor and said source of direct current potential, a branch circuit including a fifth resistor, at least first and second forward-biased semi-conductor diodes, and a sixth resistor having a resistance substantially equal to the resistance of said fifth resistor, connected in series in the order named between the collector and the emitter of said control transistor, a capacitor connected solely between the junction of said first and second diodes and the emitter of said first transistor, whereby the impedance of said branch circuit is effectively connected in parallel with said first resistor, and means to apply a direct control voltage to the base of said control transistor to vary the current through said diodes and thereby the impedance at the emitter of said first transistor, without changing the voltage thereat thereby to vary the gain of said amplifier stage.
Claim 2
Dependent Claim
255 words
A voltage-controlled variable-gain amplifier system comprising, in combination, an amplifier stage including a first transistor having a base, an emitter and a collector, means to apply an input signal to the base of said first transistor relative to ground, a first resistor connected between the emitter of said first transistor and ground, A second resistor connected between the collector of said first transistor and a source of direct current potential, a control transistor having a base, an emitter and a collector, a third resistor connected between the emitter of said control transistor and ground, a fourth resistor having a resistance substantially equal to the resistance of said third resistor connected between the collector of said control transistor and said source of direct current potential, a branch circuit including a fifth resistor, at least first and second forward-biased semi-conductor diodes, and a sixth resistor having a resistance substantially equal to the resistance of said fifth resistor, connected in series in the order named between the collector and the emitter of said control transistor, a capacitor connected solely between the junction of said first and second diodes and the emitter of said first transistor, whereby the impedance of said branch circuit is effectively connected in parallel with said first resistor, and means to apply a direct control voltage to the base of said control transistor to vary the current through said diodes and thereby the impedance at the emitter of said first transistor, without changing the voltage thereat thereby to vary the gain of said amplifier stage.
Claim 3
Dependent Claim
99 words
Apparatus in accordance with claim 1 wherein said branch circuit further includes a third forward-biased semi-conductor diode connected between said fifth resistor and said first diode and a fourth forward-biased semi-conductor diode connected between said second diode and said sixth resistor, a third transistor having a base, an emitter and a collector, means directly connecting the emitter of said third transistor to the base of said control transistor, means directly connecting the collector of said third transistor to the collector of said control transistor, and means to apply said direct control voltage to the base of said third transistor.