| 摘要 |
<p>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 min ) 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. </p> |
