| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain an oscillation circuit comprising primarily an IC capable of selecting oscillation frequency exactly and in a wide range with simplified structure. SOLUTION: Charge/discharge of an external capacitor C1 in a serial circuit between an external resistance R1 and an external capacitor C1 connected between DC power supply Vcc with specified voltage and the ground GND outside the IC 1 is switched by turning an internal resistor R2 provided in parallel with the external capacitor C1 on/off with a transistor Tr to be driven by a comparator CP from the side of the IC 1. A threshold value of charge/ discharge voltage of the external capacitor C1 in the case of the switching is exactly provided by switching and selecting two reference voltage sources V1, V2 with analog switches S1, S2 to be switched and controlled by logic output of the comparator CP. In addition, the oscillation frequency is selected in the wide range according to selection of the external resistance R1 and the external capacitor C1.</p> |
