PCB BOARD for Function Generator XR2206 DIY Kit 20Hz - 100KHz
The kit is retired - only bare PCB is sold for $7.95
XR2206 Function Generator Kit is produce high quality Sine and Triangle wave outputs with high stability and accuracy. Square wave output is open collector type and can't be calibrated because of peculiar properties of the IC.
- Frequency's: 20Hz to 100KHz in 4 ranges with fine adjust
- Waveforms: Sine, Triangle, Square
- Supply Voltage: 12V
- Supply Current: 12-20mA
- PCB Dimensions: 73 x 38 mm
- UPC Number: 635346988677
- Amplitude: 0.05 - 2V AC Peak to Peak at 12V DC
- Distortion without adjustment: 2.5%
- Distortion with adjustment: less than 1%
- Output Impedance: 600 Ohm
- Amplitude Stability: 0.5 dB
- Amplitude: 0.05 - 4V AC Peak to Peak at 12V
- Linearity: 1%
- Output Impedance: 600 Ohm
- Amplitude: 11V AC Peak to Peak at 12V
- Rise time: 250 ns at 1KHz
- Fall time: 50 ns at 1KHz
The DIY Kit has 4 steps frequency's range: (1) 20Hz-100Hz; (2) 100Hz-1KHz; (3) 1KHz-10KHz; (4) 10KHz-100KHz. You can use jumper cup or any 1 Pole 4 Position Rotary Switch for selection of the working range. The output frequency is controlled with two Rotary Potentiometers for coarse and fine adjust.
The frequency amplitude is also controlled by Rotary Potentiometer.
Sine and Triangle wave output can be toggled with jumper on the PCB or with external 1P2T switch. The Square wave has separate output on the PCB with pull up resistor.
If you can't reach a oscilloscope to calibrate the device, please do not install Symmetry Adjust potentiometer and trim Sine Adjust potentiometer to 200 Ohm before power up the kit. Sine THD without calibration is 2.5%. Sine THD with calibration is 0.5%.
The XR2206 IC has 20 ppm/C frequency stability. In our project we use polyester film capacitors to reduce temperature drifts.
The board is designed for 12V regulated power supply. You can use simple LM317 or LM7812 power supply for this project.
XR2206 is very interesting chip manufactured by EXAR and it was designed to produce sine, triangle and square wave. The output frequency has 4 ranges and you can toggle the timing capacitor C4 - C7 with a jumper or rotary selector. R6 is the coarse control and R9 is the fine control of the frequency. R3 is the amplitude control. R10 is determines the minimum amplitude level. You can do some experiments with it value.
Actually the XR2206 IC can generate up to 1MHz, but to keep good control linearity we reduce the total frequency ranges of the kit to 20Hz - 100KHz. However you are free to experiment with R5, R6 values to increase the output frequency.
R1, R2 ratio control the frequency offset and we use in the kit two 1% tolerance resistor. But you can use external rotary potentiometer 10K instead R1 and R2 to control the offset.
R7, R8 is the sine wave calibration trimmers. If you have scope you can calibrate the purity of the sine wave to 0.5% TDH. In case you can't reach a oscilloscope, then trim R8 to 200 Ohm before power on and ignore R7 installation. Without calibration the XR2206 IC can produce sine waves with 2.5% THD.
1. Set the S/T jumper to close for the sine wave output.
2. Set frequency jumper to C5 100nF.
3. Connect 12V power supply and oscilloscope probe. Power up the device.
4. Set the amplitude to the maximum with R3.
5. Set the frequency to 1KHz with R6 and R9.
6. Use a screwdriver to trim R7 to the midpoint and adjust R8 for minimum distortion.
7. With R8 set as above, adjust R7 further reduce distortion.