| Operational amplifier bistable multivibrator |
Operational amplifier bistable multivibrator
- a circuit for a bistable multivibrator using an operational
amplifier, op amp
It is easy to use an operational amplifier as a bistable
multivibrator. An incoming waveform is converted into short pulses and these are
used to trigger the operational amplifier to change between its two saturation
states. To prevent small levels of noise triggering the circuit, hysteresis is
introduced into the circuit, the level being dependent upon the application
required. The operational amplifier bistable multivibrator uses just five
components, the operational amplifier, a capacitor and three resistors.
Bistable multivibrator operational amplifier circuit
The bistable circuit has two stable states. These are the
positive and negative saturation voltages of the operational amplifier operating
with the given supply voltages. The circuit can then be switched between them by
applying pulses. A negative going pulse will switch the circuit into the
positive saturation voltage, and a positive going pulse will switch it into the
negative state.
Waveforms for the bistable multivibrator operational
amplifier circuit
It is very easy to calculate the points at which the circuit
will trigger. The positive going pulses need to be greater than Vo-Sat through
the potential divider, i.e. Vo-Sat x R3 / (R2 + R3), and similarly the negative
going pulses will need to be greater than Vo+Sat through the potential divider,
i.e. Vo+Sat x R3 / (R2 + R3). If they are not sufficiently large then the
bistable will not change state.
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