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US 4,152,675 AGranted
Crystal oscillator with adjustable duty cycle
AssigneeMotorola, Inc.
InventorWilliam B. Jett, Jr.
Life of this patent
Estimating the term…
Abstract
A crystal oscillator is provided a portion of which is fabricated in monolithic integrated circuit form. The circuit is temperature-compensated and utilizes a single 5 volt DC power supply compatible with NMOS and TTL voltage levels. The duty cycle of the oscillator may be varied between approximately 30 and 70 percent.
Claims13
An oscillator circuit having a variable duty cycle, said oscillator circuit comprising:
- a PNP transistor having its emitter coupled to a first potential and its collector coupled to a second potential;
- a first NPN transistor having its base coupled to the emitter of said PNP transistor and its emitter coupled to said second potential;
- a diode having its anode coupled to the base of said first NPN transistor and its cathode coupled to said second potential;
- a second NPN transistor having its base coupled to the collector of said first NPN transistor and to a third potential, its collector coupled to said first potential, and its emitter coupled to said second potential;
- a third NPN transistor having its base coupled to the emitter of said second NPN transistor, its collector coupled to said first potential and to an output terminal at which an output signal is generated, and its emitter coupled to said second potential;
- a piezoelectric crystal having a first terminal coupled to the base of said second NPN transistor and a second terminal coupled to said output terminal;
- first and second capacitance means coupled between said first and second terminals, respectively, of said crystal and said second potential;
- and
- means connected between the base of said PNP transistor and said first potential for varying the potential applied to said base, whereby the duty cycle of said output signal may be varied.
6 more elements
An oscillator circuit having a variable duty cycle, said oscillator circuit comprising:
- (a) a biasing circuit including
- a first transistor having its emitter coupled to a first potential and to a junction and its collector coupled to a second potential, and
- means connected between the base of said first transistor and said first potential for varying the potential V.sub.A at the base of said first transistor;
- (b) an amplifier circuit including
- a second transistor having its collector coupled to said first potential and an output terminal of said oscillator circuit and having its emitter coupled to said second potential, and
- a third transistor having its collector coupled to said first potential, its emitter coupled to said second potential and to the base of said second transistor, and its base coupled to said junction, said third transistor being rendered conductive when a potential 2.phi. is applied to its base;
- (c) a crystal feedback circuit including
- a piezoelectric crystal having a first terminal coupled to the base of said third transistor and a second terminal coupled to said output terminal, and
- first and second capacitance means coupled between said first and second terminals, respectively, of said crystal and said second potential;
- and
- (d) a reference circuit including
- resistive means having a first terminal and a second terminal, said second terminal being coupled to said junction, and
- means for providing a reference potential at the first terminal of said resistive means, said reference potential being greater than 2.phi.;
- wherein an oscillating signal having a substantially constant period is generated at said output terminal, said oscillating signal having a DC voltage component V.sub.o substantially equal to said potential V.sub.A, wherein V.sub.o exceeds said potential 2.phi. at the base of said third transistor for a relatively greater proportion of said output signal period as V.sub.A is increased, and wherein V.sub.o exceeds said potential 2.phi. for a relatively lesser proportion of said output signal period as V.sub.A is decreased.
11 more elements
Dependencies are inferred from the claim text.