The following pages contains some useful articles and projects in basic electronics.



It is a low frequency Wiew bridge sinusoidal oscillator for the audio range with very low distortion, useful to test a variety of audio equipments. The circuit has been fully tested and a PCB circuit board is available to easily mount all components.

The circuit uses only one integrated circuit, some passive components and is able to provide more than 15 V peak-to-peak or 5V RMS with a distortion less than 0.1%. In addition it uses a FET transistor to control the output amplitude and maintain it flat across the frequency range.

The oscillator uses a simple circuit to generate the following fixed frequencies in the audio range:

     20 Hz

    200 Hz

    1 KHz

    4 KHz

    8 KHz    

    16 KHz

 The simplified circuit diagram is showed in the following figure.


The output frequency is defined by the R and C values and can be calculated using the following formula:



Frequency (Hz) = ------------------                       (1)

                            6.28 x R x C




The circuit

The circuit has been designed to be simple, small and effective. A single PCB (printed circuit board) is used to hold all electronics parts.



The circuit has been designed to use a single uA747 chip that includes two op-amps inside. The first op-amp (U1A) is configured as a Wiew bridge oscillator with very low distortion. The rotary switch SW1A, B provides the connection to six different resistances and capacitor couples to cover six different audio frequencies. The operating frequency can be easily changed using the formula in 1.

Q1 operates as an AGC (Automatic Gain Control) and controls the OP-amp gain in order to maintain fixed the output signal level.

The second op-amp U1B is used as an inverting output amplifier to decouple de circuit from the load and increase the output signal up to 15 Volt peak-to-peak.

The output potentiometer P1 provides a way to control the output voltage from 0 to 15 Volt pk-pk.

Since the circuit requires only a current of 5 mA, it can be powered using two standard 9V batteries.


For those that would like to build the Wiev bridge oscillator, a professional made PCB and a complete kit with all parts is available. The PCB is small and able to accommodate all components.

PCB, containing the printed circuit board and mounting instructions

17 US$         (including shipment)
Complete KIT, containing the PCB, all electronics parts, connectors, and mounting instructions 45 US$         (including shipping)

If you are interested please send me an email: