SK Kaul and IK Kaul
EDN
The absence of a fast one-shot multivibrator in the entire TTL family, as well as the low-voltage swing and unwieldy supply requirements of ECL, drove us to exploit the fast transition times and low propagation delays of F-series gates. The application called for the implementation of a compact, portable, fast light pulser for field testing fast photomultipliers in gamma-ray astronomy work. The use of only two ICs helped to minimize the size and power consumption (Figure 1).
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| Figure 1. | This circuit provides fast light pulses in a blue LED. | |
The normally high pulses at the output gate, G4, in IC2 have rise and fall times of approximately 2.5 nsec and a duration of less than 10 nsec, corresponding to three gate delays. These pulses are ideally suited to pull low the cathode of a fast, blue HLMP-CB15-type LED with the anode clamped at 5 V. The gate forces almost the entire 5 V supply voltage across the LED. This high swing ensures optimum brightness of the LED, which is soldered to the edge of a small pc-board strip. Rechargeable batteries are clamped onto the other side of the pc board. Using a CMOS version of the timer, IC1, the circuit has a current drain of less than 4 mA.
