Amplifiers – With semiconductor amplifying device – Including gain control means
Patent
1985-06-06
1986-08-26
LaRoche, Eugene R.
Amplifiers
With semiconductor amplifying device
Including gain control means
330282, 330308, H03G 330, H03F 308
Patent
active
046085424
ABSTRACT:
A transimpedance amplifier for data signals from a high impedance source includes a forward voltage amplifier and a feedback resistance. The feedback includes an FET. The resistance of the FET is controlled by a control signal derived from the data signal at the output of the transimpedance amplifier by a differentiator which generates pulses for each data transition and an average detector which generates a control signal responsive to the number of transitions per unit time, which is the data rate. The resistance of the FET is high when the data rate is low, reducing the noise magnitude and decreasing the noise bandwidth. When the data rate increases, the resistance of the FET decreases, providing greater bandwidth for handling the signal. The change in gain caused by the bandwidth control tends to change the magnitude of the output data signal. This may be corrected by an AGC loop which controls the open loop gain of the voltage amplifier. In order to reduce the effect of differences in the bit transition time, a limiter may be coupled to the bandwidth control signal generator.
REFERENCES:
patent: 3571721 (1971-03-01), Jabbar
patent: 3999060 (1976-12-01), Skagerlund
patent: 4415803 (1983-11-01), Muoi
patent: 4540952 (1985-09-01), Williams
patent: 4565974 (1986-01-01), Smoot
patent: 4567363 (1986-01-01), Goodnough
patent: 4567446 (1986-01-01), Konoshi
Article entitled "PIN-FET Receiver for Fiber Optics", by S. A. Siegel et al., published in RCA Review, Mar. 1984, pp. 4-23, vol. 45.
Article entitled "FETS as Voltage-Controlled Resistors", by James Sherwin, published in SSD/CDE in Aug. 1965, pp. 12-14.
LaRoche Eugene R.
Meise William H.
Mottola Steven J.
RCA Corporation
Tripoli Joseph S.
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