| 摘要 |
PROBLEM TO BE SOLVED: To provide a CR oscillation circuit wherein an error in oscillation frequency does not arise in a state an external resistor is mounted. SOLUTION: An oscillation signal of a node N3 is returned to a node N1 via transistors 11 and 12 operating as return resistance. A capacitor 4 is connected between nodes N1 and N2 and an oscillation frequency is controlled by the capacitor 4 and a value of the return resistance. On the other hand, a conduction state of the transistors 11 and 12 are controlled by a voltage V20 output from a constant current circuit 20 wherein a current value is set by the external resistor R and a voltage V30 obtained by performing level shift on the voltage V20 in a level conversion circuit 30. Accordingly, the oscillation frequency is controlled by a value of the external resistor R. A current of the constant current circuit 20 is not affected by a parasitic capacity of the external resistor R, so that an error of the oscillation frequency does not arise in the state of being mounted with the external resistor R. COPYRIGHT: (C)2004,JPO
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