Zero Crossing Detector (ZCD): Comparator circuit using 741 op amp

Zero crossing detector(ZCD) is a voltage comparator that switches the output between +Vsat and –Vsat (Vsat: Saturation voltage almost equal to 14V) when the input crosses zero reference voltage. Then what is a comparator? In simple words comparators are basic operational amplifier circuits that compare two voltages simultaneously and switches the output according to the comparison. We can say zero crossing detection circuit is a comparator example. We will discuss in detail about comparator in our upcoming articles. Inverting zero cross detector circuit schematic using op amp 741 IC is shown below along with working, input output wave forms.

Zero crossing circuit diagram

Zero Crossing Detector(ZCD)

Components required

  1. Op amp
  2. Power supplies
  3. Function generator

ZCD Input and Output Waveform


Working of zero crossing detector circuit

  • Working of ZCD can be easily understood if you know the working of a basic opamp comparator.
  • In ZCD, we are setting one of the inputs as zero i.e. zero reference voltage.
  • The output is driven into –Vsat when the input signal passes through zero to positive direction.
  • Conversely, when input signal passes through zero to negative direction, the output switches to +Vsat.

Zero crossing detector applications

ZCD circuit can be used to check whether the op-amp is in good condition. Zero crossing detectors can be used as frequency counters and for switching purposes in power electronics circuits.ZCD is a basic op amp circuit.

Components Pin Out

2 thoughts on “Zero Crossing Detector (ZCD): Comparator circuit using 741 op amp

  1. Good day,
    Please I have a mopower 900VA/12V inverter which is not charging battery. When it is connected to mains, it won’t turn on the charging circuit but in inverting mode it works when connected to battery.
    What should I do to rectify this problem.

  2. may I get proper details of apparatus with their IC’s and all other info which are used for the operational amplifier Z cd

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