| 摘要 |
PURPOSE:To uniformly decide logic when the title circuit is used in the input part of a logic circuit by providing first and second emitter follower circuits whose emitters are connected by a capacitor and a no signal detection circuit. CONSTITUTION:The emitters of the first emitter follower circuit 100 and the second emitter follower circuit 200 are connected by the capacitor 7. The collector of a transistor 5 is connected to the base of a transistor 4, and the no signal detection circuit 6 is inserted and connected between the base of the transistor 5 and an input terminal 1. When no AC signal exists, the out of the no signal detection circuit 6 goes to a HIGH level, and a current flows on the collector of the transistor 5 via a resistor 12, and the base voltage of the transistor 4 drops, then, the voltage of output 2 drops. ln such a way, it is possible to decrease a DC level when no signal exists less than that when a signal exists, and to uniformly decide the logic when no signal exists when the circuit is used in the input part of the logic circuit. |
