Tsukure Mad Labs Peak Detector Circuit

Peak Detector Circuit is used to find the peak amplitude in a rapidly changing waveform. Peak detectors are generally used in the sound measuring applications to find the maximum level of sound in a particular area or place, that helps in determining the maximum loudness level in that place. So, like this there are number of applications where a Peak Detector Circuit is used. For a Basic Peak Detector Circuit, we don’t even need any complex electronics components. A Simple Peak Detector Circuit can be built by using a diode and a capacitor.

A basic peak detector circuit is a connection of a diode and a capacitor in series. The diode is placed in forward biased condition and for output, the oscilloscope probe is connected between the diode and capacitor.

Practically the output is taken across some load connected to the circuit. So, when the input signal is decreasing the capacitor starts discharging through the load RL. To hold the charge and slow down the discharging of capacitor choose the load RL of very high value.

The output of the circuit will be defined as


Where VIN is the input signal voltage and VD is the voltage drop across the diode. Here, in the output waveform, you can the see the peak is shifted down because of the voltage drop acrosss the diode in the circuit. So, this voltage drop at diode reduces the efficiency of the circuit, and to improve the design next we will use Op-amp.

For detecting the negative peak of the input signal connect the diode in the reverse condition.

Op-amp based peak detector circuit is the modification of basic peak detector circuit, used to remove the voltage drop across the diode. Whenever the applied input voltage signal is greater than the threshold voltage of the diode, the diode will get forward biased and acts as a closed switch. Here, the diode is connected in the feedback and hence the circuit works as a buffer circuit. So, whatever input is applied to the positive terminal of the op-amp will be received at the output terminal.

Components used in this module...

Find out more about the components used in this STEM Module.

Let's Get Started!

Below you will find a list of bits to gather before hand, followed by a detailed schematic. Using a breadboard lay out the components and connect them together as shown. Alternatively you can purchase this module from our shop and simply solder the components in the places indicated on the quality assured printed circuit boards provided.

What You Need...

1 9V Black Battery Box Connector Cable Battery / Battery Holder
1 4.7uF Capacitor (Polarized)
1 PCB Mount 2-Pin Screw Terminal Block Connector (Other)
1 1N4007 Diode
1 UA741 Integrated Circuit (IC)
1 3mm Red (Clear) LED
3 10K
[ Brown, Black, Black, Red ]
Resistor (0.25 Watt)

NB: Any resistor colour codes specified relate to 5 band resistor codes, the 5th band has not been shown intentionally. The 5th band indicates the resistor tolerence, we use only the highest tolerence resistors in our products.

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