US3851276A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Oscillator using controllable gain differential amplifier with three feedback circuits
Assignee: RCA Corp
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Filing: 1974-04-15
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Granted: 1974-11-26
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Expires: 1994-04-15
Abstract
Abstract A controllable gain differential amplifier includes a frequency selective first feedback path for causing the amplifier to oscillate, a non-frequency selective second feedback path for limiting the amplifier closed loop gain and a third feedback path for controlling the amplifier open loop gain. In one embodiment the feedback signal produced by the third path is degenerative and enables external amplitude modulation while in another embodiment this feedback signal is regenerative and causes selfmodulation of the oscillator.
Inventors
- 👤 L Kaplan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:55
CPC Classifications
H; H03; H03L; H03L5/00; H03B; H03B5/00; H03B5/20; H03B5/26; H03F; H03F3/00; H03F3/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
207 words
In combination: controllable gain differential amplifier means having two input terminals for receiving separate input signals, a gain control terminal and an output terminal, said amplifier producing an output signal having a sense dependent on the sense of the difference between the two input signals, said amplifier having a gain proportional to the value of a gain control signal supplied to said gain control terminal when said gain control signal is of one sense, and said amplifier having a gain less than unity when said gain control signal is of opposite sense; first and second feedback paths, each being connected between said output terminal and a separate one of said two input terminals, one path having a frequency selective attenuation characteristic, the other path having a frequency independent attenuation characteristic, said paths providing feedback signals in a sense for causing the amplifier output signal to oscillate; and a further feedback path connected between said output terminal and said gain control terminal for controlling the amplitude of said output signal, said further path including means for comparing said output signal with a reference signal and producing a difference signal, filter means for smoothing said difference signal, and means coupling the smoothed difference signaL to said gain control terminal.
Claim 2
Dependent Claim
207 words
In combination: controllable gain differential amplifier means having two input terminals for receiving separate input signals, a gain control terminal and an output terminal, said amplifier producing an output signal having a sense dependent on the sense of the difference between the two input signals, said amplifier having a gain proportional to the value of a gain control signal supplied to said gain control terminal when said gain control signal is of one sense, and said amplifier having a gain less than unity when said gain control signal is of opposite sense; first and second feedback paths, each being connected between said output terminal and a separate one of said two input terminals, one path having a frequency selective attenuation characteristic, the other path having a frequency independent attenuation characteristic, said paths providing feedback signals in a sense for causing the amplifier output signal to oscillate; and a further feedback path connected between said output terminal and said gain control terminal for controlling the amplitude of said output signal, said further path including means for comparing said output signal with a reference signal and producing a difference signal, filter means for smoothing said difference signal, and means coupling the smoothed difference signaL to said gain control terminal.
Claim 3
Dependent Claim
79 words
The combination recited in claim 1 wherein said means for comparing said output signal with a reference signal and producing a difference signal comprises: a first node; and a further amplifier, responsive to said output signal and said reference signal, for supplying a current of one sense to said first node when said output and reference signals are of first relative values, said current being of opposite sense when said output and reference signals are of second relative values.
Claim 4
Dependent Claim
65 words
The combination recited in claim 2 wherein said further amplifier comprises: a transistor having emitter, base and collector electrodes, said emitter electrode for receiving said reference signal, said base electrode being coupled to said output terminal, said collector electrode being connected to said first node; a second node for receiving an operating potential; and impedance means coupled between said first node and said second node.
Claim 5
Dependent Claim
37 words
The combination recited in claim 2 wherein said filter means for smoothing said difference signal comprises: a low pass filter, the cut-off frequency thereof being less than the frequency of the oscillations produced by said differential amplifier.
Claim 6
Dependent Claim
31 words
The combination recited in claim 4 wherein said low pass filter comprises: a circuit reference potential point; and a capacitor connected between said first node and said circuit reference potential point.
Claim 7
Dependent Claim
62 words
The combination recited in claim 4 wherein said low pass filter provides phase shift of said smoothed difference signal of a value for causing periodic variations of the envelope of the oscillations produced by said amplifier, the frequency of said periodic variations being lower than the frequency of said oscillations, said low pass filter including at least two low pass filter sections.
Claim 8
Dependent Claim
57 words
The combination recited in claim 6 wherein said low pass filter comprises: a circuit reference potential point; a first capacitor connected between said first node and said circuit reference potential point; a second node; a resistor connected between said first and second nodes; and a second capacitor connected between said second node and said reference potential point.
Claim 9
Dependent Claim
63 words
The combination recited in claim 1 wherein said controllable gain differential amplifier comprises a two-quadrant operational transconductance amplifier, said operational transconductance amplifier differentially amplifying the signals supplied to said two input terminals in proportion to values of a bias current of one sense applied to its gain control terminal and having a differential gain of substantially zero for bias currents of opposite sense.
Claim 10
Dependent Claim
59 words
The combination recited in claim 8 wherein said first and second feedback paths comprise: a circuit reference point; four resistors connecting said two input terminals, said reference point and said output terminal in a bridge configuration; and two capacitors, one in series with one of the bridge resistors and the other in parallel with another of the bridge resistors.
References Cited (Backward Citations)
US3579150A
Cited
US3805184A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-25 | 1978-05-27 | 1978-11-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-25 | 1982-05-27 | 1982-11-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-25 | 1986-05-27 | 1986-11-26 | $7700.00 | Window Closed / Lapsed |