| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an oscillation circuit capable of providing an accurate oscillation frequency even when manufactured by a CMOS process. <P>SOLUTION: A voltage Vref is converted to a current by an operational amplifier OPA1, an N-channel MOS transistor MN1 and a resistor R1 of a resistance value R, and the current is carried to a resistor R2 of a resistance value R to provide a voltage (Vdd-Vref). The voltage Vref is converted to a current by an operational amplifier OPA3, an N-channel MOS transistor MN3 and a timing resistor Rt, and a timing capacitor Ct is charged with the current to provide a voltage V<SB>OSC</SB>changing from Vdd to (Vdd-Vref). When the voltage V<SB>OSC</SB>reaches (Vdd-Vref), a comparator CMP2 turns on a P-channel MOS transistor MP2 to charge the capacitor Ct. This is repeated to provide sawtooth waves V<SB>OSC</SB>. Since a current mirror circuit is not used, an accurate oscillation frequency can be provided. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
