Gamma correction circuit

Claim 1

A gamma correction circuit comprising: amplifying means for amplifying an input signal, said amplifying means including input and output terminals; a non-linear circuit having a first terminal and a second terminal and a plurality of series-connected diode means connected between said first terminal and said second terminal, the first terminal of said non-linear circuit being coupled to the output terminal of said amplifying means and each of said diode means being connected to have the same polarity so that current flows from the first terminal to the second terminal of said non-linear circuit, wherein the voltage of a signal appearing at the first terminal of said non-linear circuit is varied non-linearly in accordance with the change in the voltage of an input signal to said amplifying means; an emitter follower circuit having an input terminal and an output terminal and a plurality of cascaded emitter follower transistors connected between said input and output terminals of said emitter follower circuit, the output terminal of said emitter follower circuit being coupled to the second terminal of said non-linear circuit, each of said emitter follower transistors being connected so that current flows from the input terminal of the emitter follower circuit to the output terminal of the emitter follower circuit, said plurality of cascaded emitter follower transistors being equal in number to said plurality of diode means; and circuit means for applying a control signal coupled to the input terminal of said emitter follower circuit, for varying nonlinearity of said input signal; whereby a change due to ambient temperature in a voltage across said non-linear circuit is compensated by a change due to ambient temperature in a voltage across said emitter follower circuit.