Oscillators – Solid state active element oscillator – Transistors
Patent
1996-04-17
1997-02-25
Mis, David
Oscillators
Solid state active element oscillator
Transistors
331108C, H03B 536
Patent
active
056062958
ABSTRACT:
A one pin on-chip crystal oscillator circuit and a method of operating that oscillator are provided. The oscillator makes use of the gate-source capacitance of a MOS transistor to provide capacitance which would otherwise need to be provided by one of two oscillator capacitors. The MOS transistor is provided with a floating well by coupling its body to its source, so that the gate-source capacitance does not change substantially when the transistor is turned off. In another aspect of the invention, the MOS transistor is provided with a floating well using a parallel combination of MOS transistor elements, so as to minimize the coupling resistance of the MOS transistor to other elements of the circuit. In another aspect of the invention, the MOS transistor is coupled to a simulated inductive circuit for assuring that the impedance of the two passive oscillator components, normally capacitors, is inductive (will not oscillate) at frequencies near the fundamental frequency of the crystal and capacitive (will oscillate) at frequencies near the third harmonic of the crystal. In another aspect of the invention, the MOS transistor is coupled to a circuit for setting its transconductance by reference to an external component.
REFERENCES:
patent: 4873498 (1989-10-01), Kleinberg
patent: 5155453 (1992-10-01), Ruetz
Ohara Harlan H.
Yiu Lee C.
Mis David
Seeq Technology Inc.
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