Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
1998-10-29
2001-03-27
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S314000, C327S320000
Reexamination Certificate
active
06208191
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to wireless communication input circuits in semiconductor devices. Specifically the present invention relates to clamping the input voltage which may be induced in the presence of strong RF fields for the purpose of preventing damage to electronics connected to the input circuit.
2. Description of the Prior Art
A wireless communication input circuit has two desirable characteristics. First, a high impedance input is needed so that power is not dissipated in the input circuit. Second, a low impedance over-voltage clamp is required so that electronic circuitry downstream of the input circuit is protected from high voltages which are induced in the presence of strong RF fields.
The current state of the art describes voltage clamps which are implemented by means of zener diodes. While there are numerous limitations to zener diodes, a primary concern are controlling fabrication parameters in RF input circuits which are implemented on a single, monolithic integrated circuit. Zener diodes also are characterized by difficulty in creating symmetrical clamping for positive and negative voltages.
Therefore, a need existed to provide a voltage clamp that will provide symmetrical positive and negative voltage clamping.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a voltage clamp for wireless input circuits which operate over the radio frequency domain.
It is another object of the present invention to provide a voltage clamp that clamps both positive and negative voltages.
It is another object of the present invention to provide a voltage clamp that clamps input voltage symmetrically in the positive and negative directions.
It is another object of the present invention to provide a symmetrical voltage clamp for both positive and negative voltages that is implemented on a single, monolithic integrated circuit.
In accordance with one embodiment of the present invention, a positive and negative voltage clamp for an input circuit is comprised of an input node, a node connected to ground potential, a MOS transistor, a diode and a capacitor which is coupled to the input node and to the control electrode of the transistor.
In accordance with another embodiment of the present invention, the MOS transistor is a P-channel transistor.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.
REFERENCES:
patent: 4423431 (1983-12-01), Sasaki
patent: 4533846 (1985-08-01), Simko
patent: 5206544 (1993-04-01), Chen et al.
patent: 5301081 (1994-04-01), Podell et al.
patent: 5528190 (1996-06-01), Honnigford
patent: 5534811 (1996-07-01), Gist et al.
patent: 5574395 (1996-11-01), Kusakabe
patent: 0 032 018 (1981-07-01), None
Jan. 25, 00 International Search Report.
Baker & Botts L.L.P.
Callahan Timothy P.
Microchip Technology Incorporated
Nguyen Hai L.
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