The circuit illustrates the usefulness of the HA-5151 as a battery-powered monostable. In this circuit, the ratio is set to .632, which allows the time constant equation to be reduced to: T=R1*C1. D2 is used to force the output to a defined state by clamping the negative input at +0.6 V. Triggering is set by C1, R3, and D2.
An applied trigger pulls the positive input below the clamp voltage, +0.6 V, which causes the output to change state. This state is held because the negative input cannot follow the change because of R,. C,. This particular circuit has an output pulse width set at approximately 100 us. Use of potentiometers for R1 and variable capacitors for C, will allow for a wide variation in T.