Temperature Stabilization of the Output Pulse Width of a Monostable Multivibrator

摘要

The width of an output pulse produced by a monostable multivibrator is a function of the circuit component values, supply voltage, and trigger pulse. In addition, the circuit component values are functions of temperature. Many applications require that the pulse width, after it has been determined by selected circuit constants, should remain constant over a reasonable range of the other variables. The objective of this study was to develop a monostable circuit having an output pulse width that was constant for reasonable variations in temperature, supply voltage, trigger-pulse amplitude and trigger-pulse width. Starting with a circuit that had been stabilized for variations in supply voltage, the output pulse width was found to be relatively independent of reasonable variations in the magnitude and duration of the trigger pulse if the trigger pulse was applied to the base of the normally nonconducting transistor. The major part of this study was devoted to the temperature variable. An expression for the pulse width as a function of temperature was derived. The values predicted by using this equation were within 1.5% of those obtained experimentally. A study of this pulse-width equation suggested stabilization and compensation methods. Applying stabilization methods, a circuit was constructed having a pulse width which varied no more than 0.85% over a temperature range of 0 to 60 exp 0 C. A compensated circuit was constructed that had no detectable change in the output pulse width over a temperature range of 0 to 60 exp 0 C. Experimental and theoretical results are included to indicate the degree of accuracy of the derived equations. The agreement between the experimental and theoretical results was very good.