Browse Prior Art Database

Sawtooth Generators with Clock Failure Protection

IP.com Disclosure Number: IPCOM000048207D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Ballatore, D: AUTHOR [+2]

Abstract

When using sawtooth generators driven by clock pulses, it is necessary to provide the generators with a protection circuit for preventing the sawtooth waveform amplitude from exceeding a predetermined maximum value when clock pulses disappear or the time period between two successive pulses becomes too long. The circuits shown in the figures are designed to clamp the generator output to a low voltage when a clock failure occurs.

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Sawtooth Generators with Clock Failure Protection

When using sawtooth generators driven by clock pulses, it is necessary to provide the generators with a protection circuit for preventing the sawtooth waveform amplitude from exceeding a predetermined maximum value when clock pulses disappear or the time period between two successive pulses becomes too long. The circuits shown in the figures are designed to clamp the generator output to a low voltage when a clock failure occurs.

In the circuit shown in Fig. 1, during normal operation, the thyristor comprised of transistors T2 and T3 is off, and a sawtooth waveform is produced at the collector of transistor T1. When voltage VS1 exceeds a threshold value equal to Vref 1 + Vbe (T2), the thyristor is latched on and capacitor C1 discharges to ground. The values of resistors R1, R2, and R3 are selected to have then VS1 approximately equal to -0.3 V to prevent the collector base junction of transistor T1 from conducting. When a clock pulse reappears, the thyristor T2-T3 is latched off by transistor T4.

In the circuit shown in Fig. 2, during normal operation, transistors T6 and T11 are off, and a sawtooth waveform is produced at the collector of transistor T5. As soon as voltage VS2 reaches a threshold value equal to Vref 2 + Vbe (T11), transistor T11 turns on, the latch comprised of transistors T7-T10 is set, and transistor T6 turns on and simultaneously clamps the sawtooth waveform amplitude to zero. As soon as a clock...