Threshold value operation circuit, and, and gate circuit, self hold circuit, start signal generation circuit using threshold value operation circuit

摘要

The invention relates to a threshold value operation circuit which can perform an analogue type threshold value operation, and which can generate an AC signal with a stabilized frequency and duty ratio which is not influenced by input signal level or characteristic changes of the circuit elements and the like. A switching device (SWa) is switched by a switching signal (Sg) from an external AC source, to modulate an input signal (Vi) which is the subject of a threshold value operation. A modulation signal (V1) thereof is level detected by a level detection circuit (10) having a previously set threshold value, and if within a range of a predetermined level, an AC output (Vo) is generated from the level detection circuit (10).