US3723894A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic gain control circuit
Assignee: GTE Sylvania Inc
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Filing: 1971-08-13
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Granted: 1973-03-27
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Expires: 1991-08-13
Abstract
Abstract VHF cascode amplifier having a PIN diode in series with its input. The RF impedance of the PIN diode varies inversely with the DC current through it. A constant DC current source including a constant current diode supplies DC current to the PIN diode. A bypass transistor has its collector connected to the constant current source and its base coupled to the amplifier output. Variations in the peak amplitude of the amplifier output cause variations in the current flow through the bypass transistor. The resulting change in DC current flow in the PIN diode changes its RF impedance so as to overcome the change in the amplifier output and maintain the output level constant.
Inventors
- 👤 R Benenati
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 06:25
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3052; H03G3/3057; H03G1/00; H03G1/0005; H03G1/0035; H03G1/0052; H03G1/0058
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
263 words
In combination RF amplifier circuit means having an input connection and an output connection; an input terminal; variable RF impedance means connected in series between the input terminal and the input connection of the RF amplifier circuit means, the value of the RF impedance of the variable RF impedance means being inversely related to the DC current passing therethrough; constant current means for providing a constant DC current; coupling means coupling said constant current means to the variable RF impedance means and providing a first DC current path through the variable RF impedance means for DC current from the constant current means; and bypass means coupled to the constant current means and to the output connection of the RF amPlifier circuit means and providing a second DC current path therethrough for DC current from the constant current means; said first DC current path through the coupling means and variable RF impedance means being in parallel with the second DC current path through the bypass means, the sum of the DC currents through the first and second DC current paths being equal to the constant DC current from the constant current means; said bypass means being operable to permit DC current from the constant current means to pass therethrough in relation to the amplitude of the signal at the output connection; whereby a change in the amplitude of the output signal from the RF amplifier circuit means changes the amount of DC current flowing through the bypass means and consequently through the variable RF impedance means thereby changing the value of its RF impedance.
Claim 2
Dependent Claim
263 words
In combination RF amplifier circuit means having an input connection and an output connection; an input terminal; variable RF impedance means connected in series between the input terminal and the input connection of the RF amplifier circuit means, the value of the RF impedance of the variable RF impedance means being inversely related to the DC current passing therethrough; constant current means for providing a constant DC current; coupling means coupling said constant current means to the variable RF impedance means and providing a first DC current path through the variable RF impedance means for DC current from the constant current means; and bypass means coupled to the constant current means and to the output connection of the RF amPlifier circuit means and providing a second DC current path therethrough for DC current from the constant current means; said first DC current path through the coupling means and variable RF impedance means being in parallel with the second DC current path through the bypass means, the sum of the DC currents through the first and second DC current paths being equal to the constant DC current from the constant current means; said bypass means being operable to permit DC current from the constant current means to pass therethrough in relation to the amplitude of the signal at the output connection; whereby a change in the amplitude of the output signal from the RF amplifier circuit means changes the amount of DC current flowing through the bypass means and consequently through the variable RF impedance means thereby changing the value of its RF impedance.
Claim 3
Dependent Claim
37 words
The combination in accordance with claim 1 wherein said variable RF impedance means includes a semiconductor diode having a value of impedance to RF signals which is inversely proportional to the amount of DC current passing therethrough.
Claim 4
Dependent Claim
104 words
The combination in accordance with claim 2 including first circuit means connected between the input terminal and the semiconductor diode for permitting the flow of RF current from the input terminal to the semiconductor diode and preventing the flow of DC current from the constant current means to the input terminal; and second circuit means connected between the semiconductor diode and the input connection of the RF amplifier circuit means for permitting the flow of RF current from the semiconductor diode to the RF amplifier circuit means and preventing the flow of DC current from the semiconductor diode to the RF amplifier circuit means.
Claim 5
Dependent Claim
91 words
The combination in accordance with claim 3 wherein said bypass means includes a bypass transistor having its collector coupled to the constant current means and its emitter connected through a control resistance to a first source of reference potential; and amplitude detection means coupled to the output connection of the RF amplifier circuit means and to the base of the bypass transistor and operable to apply a biasing voltage at the base of the bypass transistor proportional to the amplitude of the RF output signal from the RF amplifier circuit means.
Claim 6
Dependent Claim
20 words
The combination in accordance with claim 4 wherein said amplitude detection means includes a peak amplitude detector voltage doubler network.
Claim 7
Dependent Claim
109 words
The combination in accordance with claim 5 wherein said constant current means includes a constant current diode having one terminal connected to a second source of reference potential and the other terminal connected to the collector of the bypass transistor and through a resistance to the semiconductor diode; said first circuit means includes a capacitance connected between the input terminal and the juncture of the semiconductor diode and the last-mentioned resistance; and said second circuit means includes an inductance connected between the semiconductor diode and the first source of reference potential and a capacitance connected between the semiconductor diode and the input connection of the RF amplifier circuit means.
Claim 8
Dependent Claim
15 words
The combination in accordance with claim 6 wherein said semiconductor diode is a PIN diode.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |