Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Patent
1998-05-04
2000-07-04
Le, Dinh T.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Unwanted signal suppression
327553, 327552, H03K 500
Patent
active
060844655
ABSTRACT:
In this invention a time constant tuning circuit is described in which a reference clock frequency is used to adjust the gm of a transconductor and as a result the time constant of the circuit. This is done by charging a capacitor to a voltage with the current output of a transconductor during a clock period and comparing the voltage charge with another voltage. The error voltage from the comparison is used to control the gm of the transconductor. Changing the clock period changes the gm required to charge the capacitor to a voltage to satisfy the comparison. Thus the filter time constants are directly proportional to the reference clock; and therefore, are independent of process variations. The time constants can be varied by varying the clock frequency and is achieved without the use of a PLL. The output the time constant tuning circuit can be used to tune the time constants of other gm-c filters using similar transconductors and capacitors.
REFERENCES:
patent: 5325070 (1994-06-01), McGinn
patent: 5384501 (1995-01-01), Koyama et al.
patent: 5530399 (1996-06-01), Chambers et al.
patent: 5559470 (1996-09-01), Laber et al.
Ackerman Stephen B.
Le Dinh T.
Saile George O.
Tritech Microelectronics Ltd.
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