| 摘要 |
A manual override circuit for use in commercial and household electronic devices. The override circuit may employ as little as a single integrated-circuit operational amplifier, two capacitors, which are charged and discharged in appropriate sequence in response to toggling of the power supply, and several resistors. In one embodiment the manual override circuitry includes an integrated-circuit operational amplifier, which provides a high signal at its output for triggering switching circuitry to energize a load. An RC network couples low-voltage a power supply to the inverting input of the op amp. The inverting and noninverting inputs of the op amp are coupled together through a resistive network, which may be provided by single resistor. A second resistive network, which may also be provided by single resistor couples the inverting input to ground. A resistive feedback path, which may also be provided by single resistor couples the op amp output to the noninverting input, which is also coupled to ground through an additional capacitor. This simple circuit arrangement, which may consist of as little as one op amp, two capacitors, and five resistors, provides fully stable manual override operation in response to manual toggling of a switch controlling power to the device.
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