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Multivibrator Synchronization

IP.com Disclosure Number: IPCOM000098790D
Original Publication Date: 1959-Dec-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Johnson, JE: AUTHOR

Abstract

The circuit effects synchronization or retiming of a conventional transistorized multivibrator by the injection of sync pulses whose repetition rate is lower than the natural frequency of the multivibrator. Transistors T1 and T2 are connected in the conventional cross coupled manner to form a free running multivibrator. The emitter of T1 is connected to the collector of a third transistor T3, the emitter of the latter being grounded. The base of T3 is connected to the junction of resistors 4 and 5 which extend between a -12 volt source and an input terminal 6. With 6 at ground potential, the base of T3 is below ground and T3 saturates so that, in effect, the emitter of T1 is clamped to ground and the multivibrator oscillates at its natural frequency.

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Multivibrator Synchronization

The circuit effects synchronization or retiming of a conventional transistorized multivibrator by the injection of sync pulses whose repetition rate is lower than the natural frequency of the multivibrator. Transistors T1 and T2 are connected in the conventional cross coupled manner to form a free running multivibrator. The emitter of T1 is connected to the collector of a third transistor T3, the emitter of the latter being grounded. The base of T3 is connected to the junction of resistors 4 and 5 which extend between a -12 volt source and an input terminal 6. With 6 at ground potential, the base of T3 is below ground and T3 saturates so that, in effect, the emitter of T1 is clamped to ground and the multivibrator oscillates at its natural frequency.

The application of a +12 volt sync pulse to terminal 6 when T-1 is conductive (note timing diagram) cuts T3 off which in turn cuts T1 off. The multivibrator remains in this state for the duration of the sync pulse. As terminal 6 shifts to ground with the fall of the sync pulse, T3 again saturates to clamp the emitter of T1 to ground and the multivibrator starts again.

If T1 is cut off when the sync pulse occurs, T1 remains off for the duration of the sync pulse as indicated in the timing diagram. Regardless of whether T1 is conducting or not when the sync pulse is applied, resynchronization of the multivibrator is effected at the end of each sync pulse. The base electrode connection to T...