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Single Shot Multivibrator

IP.com Disclosure Number: IPCOM000098349D
Original Publication Date: 1960-Aug-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Belcastro, LE: AUTHOR

Abstract

This single shot multivibrator has an unstable state, the duration of which is varied by selectively applying gate potentials to render the various timing elements effective or non effective.

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Single Shot Multivibrator

This single shot multivibrator has an unstable state, the duration of which is varied by selectively applying gate potentials to render the various timing elements effective or non effective.

Each transistor T1... T10 has the usual three electrodes: base 11, emitter 12 and collector 13. A positive going output 14 may be taken between resistors 15 and 16, or a negative going output 17 may be taken between resistors 18 and 19.

In the quiescent state, biasing of the circuit causes the transistors to be on or off in the following combination. T1, T4, T5, T8 and T9 are off. T2, T3, T6 and T7 are on. T10 is held off when its base 11 is held at -7V (gate down). T10 is conditioned to turn on when its base 11 is held at -5V (gate up).

With the input to base 11 of T1 held at +1V, which holds T1 and T5 off, point 20 is held at about -12V through resistor 21. Diode 22 is reversely biased, blocking current through resistor 23. With point 20 at -12V, T6 and T7 conduct heavily, holding both their emitters 12 at about -12V, which is also the charge on capacitor 24 in parallel with capacitor 25 and capacitor 26 in parallel with capacitor 27.

T3, T4 and T8 form a current switch drawing their current through resistor 28 so that only one of the three may be on at one time. T1, T5 and T2 form a current switch drawing current through resistor 29 so that only one of the three may be on at one time.

Assume that the gate to base 11 of T10 is down so that T10 is held cut off. The input to base 11 of T1 is shifted from +1V to -1V causing T1 to switch on. When T1 switches on, T2 switches off and T5 remains off. When T2 switches off, the voltage between resistors 30 and 31 decreases causing T3 to cut off and allowing T4 to turn on. T8 is held cut off by the -12V across capacitor 24 applied to its base 11. When T3 and T4 switch, the output between resistors 15 and 16 rises, the output 17 from collector 13 of T4 decreases and the timed output commences.

When the input pulse at base 11 of T1 is removed, T1 switches off and T5 is turned on. A latch circuit has now been completed through T2, T3, T4 and T5.

When the input is applied at T1, turning it on, current is drawn through resistor 21 and the voltage at point 20 applied to the bases 11 of T6 and T7 rises to about -6V tending to cut off T6 and T7. The vo...