US4588968A
Expired / Lapsed
US
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Low noise constant amplitude oscillator circuit
Assignee: National Semiconductor Corp
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Filing: 1984-02-16
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Granted: 1986-05-13
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Expires: 2004-02-16
Abstract
Abstract A low noise oscillator is described suitable for use in an AM stereo radio receiver. The oscillator circuit includes means for controlling its amplitude at a constant low level. The oscillator is amenable to electronic tuning and IC construction.
Inventors
- 👤 Donald T. Wile
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 06:10
CPC Classifications
H; H03; H03L; H03L5/00; H03B; H03B5/00; H03B5/08; H03B5/12; H03B5/1206; H03B5/1209; H03B5/1231; H03B5/1237; H03B5/124; H03B5/1243; H03B5/1275; H03B5/1278; H03B2200/00; H03B2200/003; H03B2200/0058; H03B2200/006; H03B2200/0066; H03B2200/0088
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
132 words
An oscillator circuit comprising: a tank circuit; variable gain amplifier means comprising a constant G M differential amplifier driven from a variable gain differential control amplifier, said variable gain amplifier means having an output coupled to drive said tank circuit, a gain control input, and a signal input; means for coupling said tank circuit to said signal input whereby said tank circuit is caused to oscillate; level detector means, including a peak rectifier responsive to the peak level of the signal on said tank circuit, coupled to sense said tank circuit oscillation and having an output coupled to said gain control input; and means for providing a threshold level for the peak rectifier whereby said threshold level determines the amplitude of the oscillator signal and said tank circuit oscillates at constant amplitude.
Claim 2
Dependent Claim
132 words
An oscillator circuit comprising: a tank circuit; variable gain amplifier means comprising a constant G M differential amplifier driven from a variable gain differential control amplifier, said variable gain amplifier means having an output coupled to drive said tank circuit, a gain control input, and a signal input; means for coupling said tank circuit to said signal input whereby said tank circuit is caused to oscillate; level detector means, including a peak rectifier responsive to the peak level of the signal on said tank circuit, coupled to sense said tank circuit oscillation and having an output coupled to said gain control input; and means for providing a threshold level for the peak rectifier whereby said threshold level determines the amplitude of the oscillator signal and said tank circuit oscillates at constant amplitude.
Claim 3
Dependent Claim
105 words
The circuit of claim 1 wherein said variable gain differential control amplifier comprises: a pair of transistors each having an emitter, a base, and a collector; means coupling said emitters together to comprise said gain control input; means coupling said collectors of said transistors to the differential input of said constant G M differential amplifier and to low value load resistors; and resistor means coupled in parallel with the emitter-base paths of said pair of transistors whereby the tail current of said pair of transistors constitutes a fraction of the current flowing in said gain control input and the gain control response is thereby increased.
Claim 4
Dependent Claim
49 words
The circuit of claim 1 wherein said level detector comprises a high gain differential amplifier having an output coupled to supply the tail current for said control amplifier, one input coupled to a d-c reference potential and the other input coupled to receive the signal from said tank circuit.
Claim 5
Dependent Claim
21 words
The circuit of claim 3 wherein said peak rectifier is associated with said other input of said high gain differential amplifier.
References Cited (Backward Citations)
US3665342A
Cited
US3824491A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-05-12 | 1989-11-11 | 1990-05-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-05-12 | 1993-11-11 | 1994-05-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-05-12 | 1997-11-11 | 1998-05-13 | $7700.00 | Window Closed / Lapsed |