This generator produces audible indicators to check microphones and codecs utilized in audio amplifier gear. This straightforward triple sine wave generator can be used for testing different audio programs, together with VoIP (Voice over Web Protocol) gear.

The gear for transmitting speech indicators is often designed to transmit audio indicators within the vary of round 300Hz to 3400Hz. Testing of such gear is often carried out utilizing three frequencies—300Hz, 1000Hz, and 3400Hz. Through the assessments, we usually use separate and combined frequencies.

Circuit and dealing

The circuit diagram of the easy triple sine wave generator is proven in Fig. 1. It’s constructed round three twin audio operational amplifiers NE5532 (IC1 by IC3), a twin energy provide, and some different elements.

Circuit diagram of triple sine wave generator
Fig. 1: Circuit diagram of triple sine wave generator

You should utilize an operational amplifier like NE5532A, RC4560, or any comparable or higher one able to driving a great deal of as much as 600-ohm.

The circuit has three sine wave mills with Wien bridges and three operational amplifiers (IC1 by IC3). The frequencies of the oscillators are proven within the desk above.

It’s higher to make use of resistors R4 by R9 and capacitors C1 by C6 with tolerance of ±2 per cent or higher. We are able to calculate the frequency of oscillations by utilizing the formulation for the usual Wien bridge oscillator.

Pins 1 and seven of IC1 are outputs of the primary and second oscillators, respectively, whereas the output of the third oscillator is obtained from pin 7 of IC2.

All of the three indicators produced by these three oscillators are combined at IC2. Pin 1 by pin 3 of IC2 and related elements function as a sign mixer.

The amplitudes of enter indicators at pin 2 of IC2 are adjusted with potentiometers VR4, VR5, and VR6.

The triple sine wave generator has two outputs. The ahead output is buffered by first op-amp shaped by pin 1 by pin 3 of IC3, and the inverted output is buffered with second op-amp shaped by pin 5 by pin 7 of IC3. Sine wave output (O/P1) is accessible throughout CON1, and its inverted output (O/P2) is accessible throughout CON2.

The triple sine wave generator is operational in ±5V to ±15V vary, however it’s higher to make use of it with energy provide within the vary of ±7V to ±15V solely.

Building and testing

An actual-size PCB format for the triple sine wave generator is proven in Fig. 2 and its elements format in Fig. 3. Assemble the circuit on the PCB. Join ±15V twin energy provide throughout CON3, and your circuit is able to use.

PCB layout for triple sine wave generator
Fig. 2: PCB format for triple sine wave generator
Components layout of the PCB
Fig. 3: Parts format of the PCB

Obtain PCB and element format PDFs: click here

The given circuit can produce three sine-wave indicators (312Hz, 1026Hz, and 3400Hz) concurrently, as listed within the desk. These outputs can be found at CON1 and the inverted outputs at CON2 connector.

The circuit wants a easy adjustment of the amplitude for every oscillator. The potentiometers VR1, VR2, and VR3 are used to regulate the output amplitude of the oscillators round IC1 and IC2. We are able to change these potentiometers with acceptable fastened resistors.


Petre Tzv Petrov was a researcher and assistant professor on the technical College of Sofia, Bulgaria, and professional lecturer in OFPPT (Casablanca), Kingdom of Morocco. Now, he’s working as an electronics engineer within the personal sector in Bulgaria.

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