| 摘要 |
PROBLEM TO BE SOLVED: To extend a clamp control range. SOLUTION: The clamp circuit is provided with: a comparison circuit 5 comprising a comparator 7 which receives an output of a driver 3 having a load resistor 2 at an input terminal and receiving a video signal, the noninverting input of which connects to an output terminal 4 and the inverting input of which connects to a 1st constant voltage source 6, a clamp pulse input terminal 8 for giving a clamp pulse to the comparator 7, and a capacitor 9 connected between the output terminal of the comparator 7 and ground; a feedback circuit 10 where the base of an NPN transistor(TR) 13 is connected to the emitter of an NPN TR 11 whose base receives an output of the comparison circuit 5, a resistor 14 whose other terminal is connected to the emitter of the NPN TR 13, and the collector of the NPN TR 13 is connected to a resistor 2; and a limiter circuit where a resistor or a current source is connected to the emitters of a differential pair comprising NPN TRs 18, 19 whose emitters are connected in common, the base of an NPN TR 18 is connected to the base of the 2nd NPN TR 13, the collector of the TR 18 is connected to an output of the comparator 7, and the base of an NPN TR 19 is connected to a constant voltage source 16. |
