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How to Understand Op Amp Peak Detector Circuits

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Update time : 2020-06-09 13:50:12

Operational amplifiers figure the house blocks of linear integrated circuits. Op-Amps are nearly used everywhere at electronics. It is basically a voltage amplifier. As the appoint itself suggests, operational amplifiers are used to conduct the mathematical operations above the inputs applied to it. However apart from mathematical operations, it can also conduct range detection vocation with the assist of a diode and a capacitor. Op-Amp range detector is a circuit, which detects the peaks of the input voltage signal, if the previous input voltage signals has a peak, less than the grant range voltage symbol or at silly words, it detects and holds the most certain range at the input voltage signal.


1) know the basics of the operational amplifier circuits. The principle ideas listed below, helps us ought know range detector circuits at simple way.
  • Operational amplifiers cause two input terminals and one output terminal.
  • Input terminals includes inverting input station and non-inverting input terminal.
  • Inverting input produces the output, which is contrary at polarity ought that of input.
  • Non-inverting input produces the output having identical polarity because that of input.
  • Applying the certain voltage input ought the non-inverting terminal, results at a certain voltage output.

2) familiar the Op-amp range detector circuit using diode, capacitor and a MOSFET switch because shown. mixture the diode ought the output station of Op-amp and furnish the feedback path ought the Op-amp. The capacitor connected at the circuit helps at the detection of the peaks of the input voltage symbol applied. notice that the MOSFET switch and capacitor are at parallel. MOSFET switch helps at discharging of the capacitor.

3) know the direct of the different components used at the circuit. each and each component used at the circuit cause their cause contribution at range detection.
  • Diode acts because a short circuit while it's anode is more certain than cathode. accordingly while the certain input voltage is applied ought the non-inverting station the output of the op-amp becomes positive. because the anode of the diode is connected ought output terminal, the diode becomes send biased and completes the circuit. if the negative voltage is applied ought the non-inverting terminal, output becomes negative and the diode becomes contrary biased. accordingly the circuit becomes open.
  • Initially capacitor is uncharged. because the first input signal, capacitor charges ought the range appraise of the input voltage symbol and maintains that appraise because the output of the circuit. if the applied range voltage symbol is less than the previous range voltage, then the capacitor will no discover the applied peak.
  • MOSFET switch is used ought remove the capacitor. MOSFET switch helps at detecting vulgar the input peaks applied. This can be done by discharging the capacitor, after it is charged ought the range value.

4) use the input symbol ought the range detector circuit. The applied input symbol is because shown at the figure. The applied symbol has 6 peaks namely Vp1, Vp2, Vp3, Vp4, Vp5 and Vp6, having different magnitude. notice that, these peaks are no at usual pause of time.

5) Analyse the circuit and draw it's output waveform signals. The above spin shows the output of the range detector circuit at which peaks Vp1, Vp2, Vp4, Vp6 are detected and Vp3, Vp4 are no detected. also letter that MOSFET switch is no used ought remove capacitor after it is charged.
  • Vp1 causes the Op-Amp's output because positive. accordingly diode becomes send biased because it's anode is connected ought Op-Amp output which is certain and cathode ought capacitor which is at foundation potential. because the diode is send biased, the capacitor charges ought range appraise Vp1, which is detected.
  • When the circuit encounters Vp2, it's output becomes positive. Anode of the diode is connected ought the output terminal, which now has the appraise Vp2 and cathode ought capacitor which has appraise Vp1. because Vp2 is greater than Vp1 diode becomes send biased and it acts because a short circuit. therefore the capacitor charges ought the range appraise Vp2, which is detected at the circuit.
  • Vp3 is no detected at the circuit because, while Vp3 is encountered at the circuit, the anode of the diode is connected ought Vp3 (at output terminal) and cathode ought Vp2. because Vp2 is more certain than Vp3 diode becomes contrary biased. accordingly no charging of capacitor takes place. however the capacitor holds above ought its voltage flat at Vp2.
  • Circuit detects Vp4, because it is greater than the Vp2 (not only just Vp3) and charges ought Vp4 level.
  • Vp5 is no detected because the identical discuss that Vp4 is greater than Vp5 and the capacitor assert its continual voltage flat ought Vp4.
  • Vp6 is detected, because it is greater than both Vp5 and Vp6.
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