| 摘要 |
PROBLEM TO BE SOLVED: To obtain a time constant circuit which easily has a large time constant in an analog IC or a timer circuit by using an insulated gate electric field effect type transistor (MOSFET) in a reverse bias state as a capacity. SOLUTION: When a power switch SW is turned on, power supply voltage rises up to Vcc, and a signal from an AC signal source 3 is inputted to the input terminal Nin of time constant circuits 1 and 2. The although the capacitance value of a MOSFET MC2 in the forward bias state of the circuit 2 is constant from power-on the capacity value of a MOSFET MC1 in the reverse bias state of the circuit 1 rises gradually, becoming larger than the capacity value of the MC2 after a prescribed time passes, and then stabilizes at a prescribed value. The phase of a node n1 becomes faster than the phase of a node n2 immediately after power supply voltage is inputted. Them, a signal Vout, which changes from a low level to a high level at the time when the phase of the node n1 and the phase of the node n2 are reversed, is outputted from a phase detection circuit 4.
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