SN74121D

The SN74121D is a Monostable Multivibrator with schmitt-trigger inputs. It features dual negative-transition-triggered inputs and a single positive-transition-triggered input which can be used as an inhibit input. Complementary output pulses are provided. Pulse triggering occurs at a particular voltage level and is not directly related to the transition time of the input pulse. Schmitt-trigger input circuitry (TTL hysteresis) for the B input allow jitter-free triggering from inputs with transition rates as slow as 1V/s, providing the circuit with an excellent noise immunity of typically 1.2V. A high immunity to VCC noise of typically 1.5V is also provided by internal latching circuitry. Once fired, the outputs are independent of further transitions of the inputs and are a function only of the timing components. Input pulses may be of any duration relative to the output puls. Output pulse length may be varied from 40ns to 28s by choosing appropriate timing components.