PCB BOARD for Function Generator XR2206 DIY Kit 20Hz - 100KHz

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Very simple DIY Kit of Function Generator based on XR2206 IC. The circuit was taken from the datasheet and adapted to our project condition.

The kit is not require calibration! But also has components included in case you want to have full control on it with an oscilloscope for calibration to 0.5% THD.

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.

Technical Specification:

  • 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 

Sine Wave:

  • 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

Triangle Wave:

  • Amplitude: 0.05 - 4V AC Peak to Peak at 12V
  • Linearity: 1%
  • Output Impedance: 600 Ohm

Square Wave:

  • 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 Kit is designed for 12V regulated power supply. You can use simple LM317 or LM7812 power supply for this project.

Package include:

1x Manufactured 2 Layers High Quality PCB 73x38 mm

1x XR2206CP IC

2x 1% Metal Film Resistor 5.1K

1x 1% Metal Film Resistor 10K

1x 1% Metal Film Resistor 10R

1x 1% Metal Film Resistor 3K

1x Trimmer Potentiometer top adjust 500R

1x Trimmer Potentiometer top adjust 30K

2x Rotary Potentiometer 10K

1x Rotary Potentiometer 100K

1x 1N4007 Diode

1x 100uF Electrolytic Capacitor 35V

1x 10uF Electrolytic Capacitor 35V

1x 1uF Electrolytic Capacitor 35V

1x 100nF Ceramic Capacitor 50V

1x 1nF Polyester Film Capacitor 63V

1x 10nF Polyester Film Capacitor 63V

1x 100nF Polyester Film Capacitor 63V

1x 1uF Polyester Film Capacitor 63V

1x DIP Socket 16 Pin

2x Jumper Cup

20x Pin of 2.54 mm Male Pin Header

3x Washer for Rotary Potentiometer

3x Nut for Rotary Potentiometer

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.

Calibration flow:

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.

XR2206 DIY Function Generator Circuit

Take note, R4-10K need to be replaced with 1K resistor to improve square wave rise time on high frequency operation!

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