Amplifiers – With control of power supply or bias voltage – With control of input electrode or gain control electrode bias
Patent
1988-09-09
1989-09-05
Mullins, James B.
Amplifiers
With control of power supply or bias voltage
With control of input electrode or gain control electrode bias
330136, 330149, 330281, 381107, 455238, 455244, H03G 330
Patent
active
048642460
ABSTRACT:
An automatic volume control apparatus for use in a mobile audio apparatus in which a detection output from a noise detection section is compared with a control output applied to a volume control section, and a capacitor inserted between a control signal input terminal of the volume control section and a reference voltage point is charged/discharged by a current source section with a constant current on the basis of the output of the comparator to thereby make it possible to make the change of volume constant or linear relative to the change of noise level. Also, a control signal for a volume controller is obtained by subtracting a quantity of logarithmic change of an audio signal detection signal obtained from an audio signal detection section relative to a reference value from a value obtained by amplifying, with an amplification factor in a range of 1.5 to 2.5, a quantity of logarithmic change of a noise detection signal obtained from a noise detection section relative to a reference value, whereby the correspondence between levels of low-frequency components of, for example, 10 Hz or less and audible frequency components of in-vehicle noise becomes higher so that it is possible to perform more natural volume control.
REFERENCES:
patent: 4179667 (1979-12-01), Bottcher
patent: 4644292 (1987-02-01), Kunugi et al.
German Search Report, #P38 30 423.6 dated Dec. 12, 1988.
Patents Abstracts of Japan, E-237, Apr. 10, 1984-vol. 8/No. 78.
Kato Masayuki
Kato Shinjiro
Tamura Fumio
Mullins James B.
Pioneer Electronic Corporation
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