variable pulse width generator

7-74 elektor july/august 1980 This simple little circuit will find a great many uses where pulse width is critical. Opamp Al is connected as a squarewave generator whose fre- quency can be adjusted by poten- tiometer P2. Let us assume that the output of the opamp goes high when the system is first switched on. Part of that output voltage is fed to the non-inverting input via the voltage divider R4, P2, R3. As long as Cl is not yet sufficiently charged, the voltage at the inverting input will be lower than that at the non-inverting input and the output will remain high. The moment that the capacitor is charged to such an extent that the voltage at the inverting input becomes greater than that at the non-inverting input, the output of the opamp will swing low. Capacitor Cl then starts to discharge until the voltage at the inverting input becomes lower than that at the other input, whereupon the opamp output will swing high once more. +15V P1 +6-1 78 variable pulse width generator D1...