| 摘要 |
PROBLEM TO BE SOLVED: To provide an oscillation circuit in which oscillation frequency can be corrected with regard to production variation in threshold voltage of MOS transistors. SOLUTION: A p-type transistor P4 of the same conductivity type as that of the input inversion transistor of an inverter circuit constituting a ring oscillator OSC is diode connected and grounded through a first resistor R1. A constant current is then fed from a constant current source I1 and a turn-on voltage following the threshold voltage variation due to production variation is obtained. The turn-on voltage is fed through an operational amplifier A1 to the gate of a p-type transistor P6 and utilized for controlling a current being fed to the ring oscillator OSC through current mirrors formed by n-type transistors N1, N2 and N3 in the n-type transistor N0 and the inverter circuit. COPYRIGHT: (C)2006,JPO&NCIPI
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