Gamma correction circuit

Details Gamma correction circuit Gamma correction circuit

1987-03-04

1989-07-11

Miller, Stanley D.

Electrical transmission or interconnection systems

Nonlinear reactor systems

Parametrons

307491, 358 32, 358164, 330257, H03K 522, H04N 964

Patent

active

048475246

ABSTRACT:
A gamma correction circuit is formed with several differential amplifiers (6-10) and (11-15) each being capable of being driven into saturation with a different saturation current supplied by a current source at a different signal value (Vx and Vw, respectively) in an input signal (PV). The non-linearly changing output currents of the differential amplifiers are added with the aid of a current-mirror circuit (16-21) which is also active as a supply circuit for the differential amplifiers. The gamma-corrected output signal (PV') is obtained across a resistor (22) connected to a connection (17) of the current-mirror circuit. In the case of a changing temperature, a temperature compensation is required. To this end, the negative temperature coefficient at the base-emitter threshold voltage (Vbe) of current source transistors (8, 13) of the differential amplifiers is utilized via an adjustable voltage source (23-27), which leads to a positive relative temperature coefficient for the current of the current sources (8, 9), (13, 14) compensating the negative relative temperature cofficient at the transfer characteristic at the differential amplifiers.

REFERENCES:
patent: 3708693 (1973-01-01), Ferrier
patent: 4480268 (1984-10-01), Osawa et al.
patent: 4529893 (1985-07-01), Nagano
patent: 4558363 (1985-12-01), Sugimoto
patent: 4589021 (1986-05-01), Sato et al.
patent: 4651210 (1987-03-01), Olson

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