Function Generator

The FunGen Function Generator design utilises the Exar 2206 IC to produce Sine, Triangle and Square waves with adjustable frequency. Its features include:

Output Waveforms: TTL Square Wave and selectable Sine or Triangle Wave

Output Amplitude: Square Wave: TTL Output, Sine/Triangle: 0Vp-p to approximately 6Vp-p.

Output Frequency: 25Hz to over 250kHz 

The design 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.

Schematic:

Components Required:

IC1,   XR2206 

IC3,   LM741 or LM318 Op Amp

IC2,   74xx04 Hex Inverter

IC4,   LM7812

IC5,   LM78L05

C1,   100uF (or 10uF) Capacitor

C2,C5,C6,C7,C10,  1uF Capacitor

C3,C4,   0.1uF Capacitor

C8,   0.22uF Capacitor

C9,   2.2nF Capacitor

D1,   1N4001 Diode

R4,   200Ω 1% Resistor

R1,R5,R7,   1kΩ Resistor

R2,R3,R6,   10kΩ Resistor

R8,R9,   100 Ω Resistor (optional)

pot1, pot3,   50kΩ Pot

pot2,   250kΩ Pot

two Sliding Switches

3mm or 5mm LED

two,   Dual Screw Terminal