Adjustable contrast compressor

Details Adjustable contrast compressor Adjustable contrast compressor

1980-10-31

1982-12-28

Mullins, James B.

Amplifiers

With d.c. reinsertion circuit

330 86, 330282, 358 32, 358164, 358169, H04N 904, H03G 330

Patent

active

043664407

ABSTRACT:
A feedback amplifier is configured as a contrast compressor for video signals including a reference blanking level. A feedback resistance is divided into two resistors coupled at a juncture. Contrast compression is accomplished by a diode coupled to the juncture and to a voltage source which may be adjusted to vary the point of onset of compression. The diode current perturbs the operating point of the amplifier, thereby producing a condition in which the blanking level at the output is other than zero volts. This is undesirable as it may affect following circuits adversely or require further setup. A clamp is coupled to the inverting input terminal for offsetting the perturbation of the amplifier operating point caused by the diode current.

REFERENCES:
patent: 3543169 (1970-11-01), Hill
patent: 3684825 (1972-08-01), Dischert et al.
patent: 3714602 (1973-01-01), Macey
patent: 4126884 (1978-11-01), Shanley
Graeme, Applications of Operational Amplifiers-Third-Generation Techniques, McGraw-Hill, 1973, pp. 36-37, 96-97, 147, 217-218.
Graeme, et al., Operational Amplifiers-Design and Applications, McGraw-Hill, 1971, pp. 251-254.
Jung, I. C., Op-Amp Cookbook, Howard W. Sams, 1977, pp. 213, 399.

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