FunGen v2 Schematic

The redesign includes a buffered virtual ground circuit provided by an LM741, LM318 or similar Op Amp, which sets a fixed voltage half way between the input voltage and ground. This is then used as the virtual ground for the sine and triangle wave outputs from the "WAVE_OUT" connector, providing an output centred around 0V.

A 74HC04 or 74LS04 Hex Inverter is used to buffer the Square Wave output, decreasing the rise and fall time of the square wave output.

The amplitude and frequency adjustment pots are mounted on the board for easy adjustment. An ON/OFF switch, Waveform selector switch and Frequency range switch are also mounted on the board.

Finally, the power supply is from a 14.5V or higher AC or DC wall wart adaptor. There is a protection diode in place to rectify an AC input, and protect against reverse polarity DC. A 7812 voltage regulator is used to supply the Op Amp and XR2206 IC's, and a 78L05 is used to supply the hex inverter IC.

The outputs are short circuit and over current protected by the output IC's. As the load increases on the Sine/Triangle wave output, the output voltage decreases to remain in safe limits.