Amplifiers – With control of power supply or bias voltage – With control of input electrode or gain control electrode bias
Patent
1985-07-31
1986-09-02
Mullins, James B.
Amplifiers
With control of power supply or bias voltage
With control of input electrode or gain control electrode bias
330149, 330305, 381 29, 381 94, 381106, H03G 902
Patent
active
046098780
ABSTRACT:
A noise reduction system including a signal path (34) between an input terminal (12) and an output terminal (36), a voltage control amplifier (38) and a control path (40) between the input terminal and the voltage control amplifier is disclosed. A nonlinear element such as a voltage squarer (32) is in the controlled path. In one arrangement, the control path also includes a signal level detector (22), a one-pole high pass filter (16) and a direct current level shifter (26). A precision diode (30) is interposed in the control path between the direct current level shifter and the signal squarer. One form of the noise reduction system includes a voltage-controlled low pass filter (20) interposed in the signal path between the input terminal and the voltage-controlled amplifier. A weighing control path (46) provides the control signal for the voltage-controlled low pass filter. A two-pole high pass filter (18) followed by a level sensor (48) is interposed in the weighting control path.
REFERENCES:
patent: 3732371 (1973-05-01), Burwen
patent: 3815039 (1974-06-01), Fujisawa et al.
patent: 3980964 (1976-09-01), Grodinsky
patent: 4136314 (1979-01-01), Blackmer et al.
patent: 4169219 (1979-09-01), Beard
patent: 4250470 (1981-02-01), Szarvas
Blackmer, "A Wide Dynamic Range Noise Reduction System," reprinted from DB, Aug.-Sep. 1972, vol. 6, No. 8.
Gorin, "Hi-Fi, Noise Filter/Range Expander", Radio-Electronics, Mar. 1981, pp. 41-44, 110.
Circuit Research Labs, Inc.
Mullins James B.
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