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Delayed Single Shot

IP.com Disclosure Number: IPCOM000079957D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Hernandez, PH: AUTHOR [+4]

Abstract

This circuit generates a delayed and calibrated pulse at the output 0, whenever its input voltage Vin is up for longer than a given time. Transistor circuits T1, T2, T3 and T5 operate as current generators providing currents I1, I2, I3 and I4 equal in value, respectively.

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Delayed Single Shot

This circuit generates a delayed and calibrated pulse at the output 0, whenever its input voltage Vin is up for longer than a given time. Transistor circuits T1, T2, T3 and T5 operate as current generators providing currents I1, I2, I3 and I4 equal in value, respectively.

In the idle state, Vin is at low-logic level. Transistor T8 is off and T9 saturates. Most of current I1 flows through R13, diode D4 and transistor T9. A low level on the base of T10 turns the later off, and T11 saturates. Capacitor C is discharged through T11. Current switch T12, T13, T14 the threshold of which is Vref = R10 x I4, is maintained with T12 off and T13 on. The emitter current of T6 flows through T13, turning T7, T17 and T18 off.

Now suppose that Vin goes high. This up level applied to the base of T8 turns it on; therefore, T9 is turned off, T10 saturates and T11 turns off. Consequently, capacitor C is linearly charged by constant current I2 through R3, R'3 and D3. However two different situations may occur depending upon the time duration of the occurrence of the up level on the circuit input. For short Vin,
i.e., noise signals, C is not charged enough to reach Vref and the current switch T12-T13 is maintained in its idle state. Furthermore, as soon as Vin goes down T6 saturates and C is very quickly discharged, which avoids any undesired switching of the current switch by a cumulative effect of noise signals applied to the circuit input.

For longer Vin, C charges up to Vref, T12 is turned on while T13 is turned off. T6 current saturates T7; T...