Posted on Mar 3, 2013 3472
The input voltage, V1, causes C1 to charge and produce a ramp voltage at the output of the 741 op amp. Diodes D1 and D2 are four-layer devices. When the voltage across C1 reaches the breakover voltage of either diode, the diode conducts to discharge C1 rapidly and the op amp output goes abruptly to zero. This rapid discharge action applies a narrow pulse to G1 and G2. Positive discharge pulses produced by a positive V1 are coupled to the output only through G1, while negative pulses are coupled only through G2.
Because of the forward breakover current of diodes D1 and D2, the circuit won"t operate below a minimum input voltage. An increase of R1 increases this minimum voltage and reduces the circuit"s dynamic range. The minimum input voltage with R1 at 1 Kn is in the range of 10 to 50 m V. This input dead zone, when input signal V1 is near zero is desirable in applications that require a signal to exceed a certain level before an output is generated.