Enhanced Q current mode active filter

Details Enhanced Q current mode active filter Enhanced Q current mode active filter

1988-01-04

1989-06-27

Mullins, James B.

Amplifiers

With semiconductor amplifying device

Including differential amplifier

330294, 330305, 330306, H03F 345

Patent

active

048433438

ABSTRACT:
A current mode active filter includes a differential amplifier, having two transistors, and a current mirror, having two transistors, connected into a feedback loop. The phase shift of the loop is controlled by one or two grounded capacitors and bias current sources connected to forward bias the base-emitter junctions of the transistors. The frequency of the filter is controlled by varying the dynamic resistances of the base-emitter junctions with the bias current sources. The current mirror increases loop gain, thereby enhancing the Q of the circuit. Improved dynamic range and large-signal performance can be achieved by the addition of two transistors to the current mirror circuit.

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"Simple Electronically Tunable 2nd-Order Active Filter", Electronic Letters, vol. 13, No. 9, J. B. Grimbleby, Mar. 30, 1977.

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