Amplifiers – Signal feedback – Variable impedance in feedback path varied by separate...
Patent
1981-04-28
1983-08-09
Mullins, James B.
Amplifiers
Signal feedback
Variable impedance in feedback path varied by separate...
330136, 330141, 330281, 333 14, H03G 706
Patent
active
043981577
ABSTRACT:
In a signal expander, the envelope of an input signal to be expanded is detected and applied as a control signal to the gain control input of a variable gain device which expands the input signal. The control signal is applied to the variable gain device via an adaptive filter having improved ripple reduction and transient performance characteristics to minimize audibility of gain changes. The adaptive filter includes a low pass filter for producing a smoothed control signal essentially free of ripple and an analog gate for coupling the greater of the smoothed signal or a further signal to the variable gain device, the further signal being equal to the detector output signal less a constant. Compression of an input signal is provided by applying the input signal to the non-inverting input terminal of an amplifier and coupling the (compressed) output signal of the amplifier to its inverting input terminal via the expander.
REFERENCES:
patent: 3732371 (1973-05-01), Burwen
patent: 3980964 (1976-09-01), Grodinsky
patent: 4024463 (1977-05-01), Pelley
patent: 4114115 (1978-09-01), Minnis
patent: 4220929 (1980-09-01), Talbot et al.
patent: 4307348 (1981-12-01), Nicholson
Pickering, "High Fidelity Volume Expander", Audio Engineering, Sep. 1947, pp. 122-124.
Coalter R. G.
Mullins James B.
RCA Corporation
Tripoli J. S.
Whitacre E. M.
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