Variable capacitance circuit

Details Variable capacitance circuit Variable capacitance circuit

1998-06-19

2000-05-09

Lee, Benny

Oscillators

Solid state active element oscillator

Transistors

331177R, 330252, 334 11, H03B 508

Patent

active

060609567

ABSTRACT:
The invention provides an improved variable capacitance circuit which is substantially linearly controlled using voltage or current control. The circuit comprises two emitter connector transistors and a constant current source or drain forming a current steering circuit. A fixed capacitor is connected to the emitters of the transistors forming a port into the circuit. AC current into the port flows through the fixed capacitor and is fed back through the transistors in a proportion depending on the voltage at their bases. The effective capacitance of the circuit is varied using this variable AC feedback arrangement. Other embodiments use current control to vary the circuit capacitance by varying the effective constant current source level.

REFERENCES:
patent: 2980768 (1961-04-01), Ehret
patent: 3832656 (1974-08-01), Ito et al.
patent: 4267518 (1981-05-01), Davis
patent: 5331478 (1994-07-01), Aranovsky
patent: 5510755 (1996-04-01), Kodrnja et al.
patent: 5856763 (1999-01-01), Reeser et al.
Wei-Zen Chen and Jieh-Tsorng Wu, "A 2 V 2 Ghz BJT Variable-Frequency Oscillator" Proceedings of the 1997 Bipolar/BiCMOS circuits and Technology Meeting. Pp61-63.
Nhat M Nguyen and Robert G Meyer, "A 1.8 GHz Monolithic LC Voltage-Controlled Oscillator", IEEE Journal of Solid-State circuits, vol. 27, No. 3, pp. 444-450, Mar. 1992.

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