This transistorized, astable multivibrator is stopped by applying a pulse of proper polarity to the collector of either transistor. Afterwards, astable operation of the multivibrator is restored by applying a suitable pulse to the base of either transistor.
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Astable Multivibrator
This transistorized, astable multivibrator is stopped by applying a pulse of
proper polarity to the collector of either transistor. Afterwards, astable operation
of the multivibrator is restored by applying a suitable pulse to the base of either
transistor.
The multivibrator circuit is the two transistor, collector base coupled type.
The initial stable condition for the multivibrator is with transistors 10 and 12
conducting. When a pulse is applied to either base lead 14 or 16, the circuit
commences to cycle, in part due to the charging and discharging of capacitors 18
and 20. When a negative pulse is applied to the collector of either transistor, the
non-conducting transistor is turned on so that both transistors conduct. Upon
release of the collector pulse, both transistors remain conducting and the circuit
returns to the initial stable condition and terminates astable operation. In this
state, with base voltages at about -.25 volts and collector voltages at about -.15
volts, both junctions of each transistor are forwardly biased. This is a stable
situation requiring outside disturbance for return to astable operation.
The same operation is obtained with an astable multivibrator employing NPN
transistors. In this case, the polarities of the supplies and input signals are the
reverse of those for the PNP multivibrator.
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