Introduction

An Audio Peak Detector is an essential circuit in audio signal processing that identifies the highest amplitude or peak level of an incoming audio signal. This project utilizes the LMV358, a low-voltage, low-power dual operational amplifier, to create a compact and efficient audio peak detection system.

For Full Project:

https://electronicsworkshops.com/2025/04/28/audio-peak-detector-using-lmv358/

PCB Manufacturer

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Working Principle

Audio Input (from Mic/Line-In):

An electric microphone or audio input signal is fed into the circuit.

The signal is usually AC (alternating current), fluctuating based on sound intensity.

Amplification Stage (Using LMV358):

The LMV358 amplifies the weak audio signal.

One op-amp in the LMV358 IC can be used as a pre-amplifier to boost the audio signal.

Gain can be controlled using external resistors.

Rectifier and Peak Detection:

The second op-amp is configured as a precision rectifier and peak detector.

The output of the op-amp charges a capacitor through a diode.

This capacitor holds the peak voltage for a short duration, representing the highest amplitude of the audio signal.

Indicator (LED or ADC output):

A LED may be connected to indicate peak detection (lights up when sound is loud).

Optionally, the output voltage can be sent to a microcontroller’s ADC to display audio levels on a bar graph, VU meter, etc

Circuit Diagram

This circuit is an electret microphone preamplifier that amplifies weak audio signals and then processes them into a varying DC voltage. An electret microphone (Q1) converts sound into an electrical signal, which is then capacitively coupled (C1) to an LMV358IDR operational amplifier (U1), configured with feedback (R3) for amplification. The amplified audio signal is then half-wave rectified by a diode (D2), and the resulting pulsating DC is smoothed by capacitors (C2, C3) and a resistor (R5), effectively acting as a peak or envelope detector, with the discharge time of C3 through R5 determining how quickly the output responds to changes in audio amplitude, as indicated by the provided discharge time formula. Finally, the processed output is made available through a 3-pin header (P1) along with the power supply and ground connections.

Applications

Audio level visualization (e.g., VU meters).

Sound-activated circuits (clap switches, volume indicators).

Microcontroller-based audio sensing.

DIY audio and LED projects.

Conclusion

The LMV358 Audio Peak Detector SMD is a simple yet effective circuit to detect audio signal peaks. It uses the LMV358 op-amp to amplify and rectify the signal, storing the peak voltage which can trigger indicators or be read by a microcontroller. It’s ideal for hobbyist audio visualizations or sound-sensing automation systems.

For Full Project:

https://electronicsworkshops.com/2025/04/28/audio-peak-detector-using-lmv358/