H - Electricity – 04 – N
Patent
H - Electricity
04
N
350/46, 350/80
H04N 5/202 (2006.01)
Patent
CA 1272797
Abstract: "Gamma correction circuit". The 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 currents of the current sources (8, 9), (13, 14) compensating the negative relative temperature coefficient at the transfer characteristic at the differential amplifiers.
531222
Menting Johannes M.
Van Rooy Johannes H.j.m.
Fetherstonhaugh & Co.
Menting Johannes M.
N.v. Philips Gloeilampenfabrieken
Van Rooy Johannes H.j.m.
LandOfFree
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