Multivibrators are two-state (high or low) output circuits.
These include oscillators, timers and flip-flops. Multivibrators
are mostly used in applications which involve timing, pulse
generation or pulse triggering of other device and so on. There
are three types of multivibrators, these are monostable,
bistable and astable. 'mono' means one or single, therefore
monostable multivibrator is a single-stable state multivibrator
with other state unstable or transient. A triggering
signal/pulse is needed for this circuit to change to its
unstable state which last for a fixed period preset by timer
components of the circuit before returning to its stable state.
This circuit finds application in a system where a timing period
of fixed duration is needed in response to external event.
Monostable multivibrator circuit Above is a BJT collector-cross-
coupled monostable multivibrator circuit. At the instance of
power up, the base of transistor T2 is connected to supplied
voltage via the biasing resistor, R2 hence T2 is