| 摘要 |
PROBLEM TO BE SOLVED: To provide a time constant circuit having less variations in time constant. SOLUTION: The time constant circuit has a pnp transistor Q1, a pnp transistor Q2, a current source 1, an initializing circuit 4, a charging capacitor 5, and a reference voltage source 6. In this time constant circuit, the circuit 4 has the capability of selectively providing two functions of fixing a potential Vc of the capacitor 5 to a ground potential and preventing the influence on the charging capacitor, the emitter of the transistor Q1 and the emitter of the transistor Q2 are connected to the current source 1 in which a current varies in proportion to the increase/decrease in a current amplification factor of the pnp transistors, a reference voltage Vref of the reference voltage source 6 is connected to the base of the transistor Q1, the capacitor 5 and the circuit 4 are connected to the base of the transistor Q2, and the collector current of the transistor Q1 or the collector current of the transistor Q2 is outputted. COPYRIGHT: (C)2004,JPO
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