US3852522A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable q if amplifier
Assignee: Thomas International Corp
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Filing: 1973-05-21
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Granted: 1974-12-03
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Expires: 1993-05-21
Abstract
Abstract An Intermediate Frequency amplifier in a television receiver uses a dual gate field-effect transistor with an unbypassed source resistor. The dual gates are connected to a source of composite television signal and to a source of an automatic gain control signal. For weak signal conditions, the automatic gain control signal produces negative voltage feedback across the unbypassed source resistor, varying the output impedance of the field-effect transistor which is in parallel with a tuned circuit. The change in output impedance changes the Q of the tuned circuit and changes the response curve of the Intermediate Frequency amplifier.
Inventors
- 👤 J Martin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 19:28
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/4446
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
159 words
In a television receiver including an intermediate frequency amplifier for amplifying a modulated sound carrier and a modulated video carrier, and an automatic gain control stage for generating an AGC signal representative of the strength of a received television signal, the improvement comprising: a field-effect transistor having a gate, a source, and a drain; a tuned network coupled to said drain for passing an amplified IF signal; an unbypassed source resistor coupled to said source for generating negative voltage feedback to vary the output impedance at the drain in response to signal changes at the gate; composite signal input means for varying the current flow between the drain and source in response to the received television signal; and AGC input means for coupling the AGC signal to said gate to vary the output impedance of said field-effect transistor in response to changes in the AGC signal, whereby changes in the output impedance change the Q of the tuned network.
Claim 2
Dependent Claim
159 words
In a television receiver including an intermediate frequency amplifier for amplifying a modulated sound carrier and a modulated video carrier, and an automatic gain control stage for generating an AGC signal representative of the strength of a received television signal, the improvement comprising: a field-effect transistor having a gate, a source, and a drain; a tuned network coupled to said drain for passing an amplified IF signal; an unbypassed source resistor coupled to said source for generating negative voltage feedback to vary the output impedance at the drain in response to signal changes at the gate; composite signal input means for varying the current flow between the drain and source in response to the received television signal; and AGC input means for coupling the AGC signal to said gate to vary the output impedance of said field-effect transistor in response to changes in the AGC signal, whereby changes in the output impedance change the Q of the tuned network.
Claim 3
Dependent Claim
54 words
The improvement of claim 1 wherein said field-effect transistor includes a first gate and a second gate each responsive to vary the current flow between said source and drain, said first gate being coupled to said AGC input means, and said composite signal input means couples the received television signal to said second gate.
Claim 4
Dependent Claim
16 words
The improvement of claim 2 wherein said field-effect transistor comprises a dual gate, metal-oxide-semi-conductor field-effect transistor.
Claim 5
Dependent Claim
41 words
The improvement of claim 1 wherein said tuned network comprises a single tuned network coupled between the drain of said field-effect transistor and a second IF amplifier, said single tuned network being tuned to the frequency of the modulated video carrier.
Claim 6
Dependent Claim
50 words
The improvement of claim 4 wherein the field-effect transistor of the first amplifier and the second IF amplifier are stagger tuned to provide an overall response characteristic which peaks in the vicinity of the video carrier for a change in Q produced by a received television signal of weaker strength.
Claim 7
Dependent Claim
52 words
The improvement of claim 5 wherein said second IF amplifier includes a field-effect transistor having a gate, a source, and a drain, said gate being coupled to said single tuned network, said drain being coupled to a utilizatioN means, and said source being coupled to a source resistor bypassed by a capacitor.
Claim 8
Dependent Claim
64 words
The improvement of claim 1 including a DC potential supply and a ground reference, said unbypassed source resistor being coupled between said source and said ground reference, said tuned network comprises a first reactive impedance coupled between said drain and said DC potential supply and a second reactive impedance in shunt with said field-effect transistor and coupled between said drain and said ground reference.
Claim 9
Dependent Claim
37 words
The improvement of claim 7 wherein said first reactive impedance comprises an inductor and said second reactive impedance comprises a capacitor, said inductor and capacitor being tuned approximately to the frequency of one of said modulated carriers.
References Cited (Backward Citations)
US3495031A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-02 | 1978-06-03 | 1978-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-02 | 1982-06-03 | 1982-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-02 | 1986-06-03 | 1986-12-03 | $7700.00 | Window Closed / Lapsed |