How to build a function generator - Page 1
Forum section: electronics / projects

author: Abayomi
author_rank: Contributor
timestamp: May 19, 2016, 01:14:28 am
content: Please someone should help me out. I want to build a function generator, I need the circuit diagram of a workable one

author: danadak
author_rank: Super Contributor
timestamp: May 19, 2016, 01:58:53 am
content: There are quite a few ways.What are the specs you want, frequency range, drive power or laod, amplitude, distortion ?http://www.edn.com/design/analog/4364021/Function-generator-has-variable-frequencyRegards, Dana.

author: Rerouter
author_rank: Super Contributor
timestamp: May 19, 2016, 02:25:23 am
content: Also depends on what approaches your comfortable with,E.g my most recent approach was a AD9850 DDS module off ebay, and a cheap micro, Mainly because i couldnt beat if for the frequencies i was after,

author: MrSlack
author_rank: Frequent Contributor
timestamp: May 19, 2016, 07:48:38 am
content: Look for the Exar XR2206 IC application notes book on archive.org. There's a whole lab function generator schematic in there. I used one built from that for about 20 years until I got a new Thandar one a few weeks back.Forget DDS if you're starting out - very complicated solution.

author: MrSlack
author_rank: Frequent Contributor
timestamp: May 19, 2016, 10:14:15 am
content: XR2206 IC (ebay, dirt cheap), a couple of capacitors, two 9v batteries or a dual rail supply, two pots, plus a 220 ohm resistor. Nope, dead simple.Or you could build a current source/sink pair then integrator then comparator then sine shaper. But Exar already did all that for you.

author: danadak
author_rank: Super Contributor
timestamp: May 19, 2016, 10:47:18 am
content: You need to answer this -"What are the specs you want, frequency range, drive power or load (50 ohms for example), amplitude, distortion, resolution ?"Without that forum simply guessing a lot about what you need. Eg, do you want it to power the city of NewYork or .....Regards, Dana.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 19, 2016, 03:33:33 pm
content: Both the DDS Chip and the analog (e.g. XR2206) type have there advantages and weak points:The analog solution is rather simple, gives a reasonable triangle and the option to do amplitude and frequency modulation and frequency sweeps if you want to. However the frequency is not very stable, sine quality is limited and the frequency range of the XR2206 is limited to something like 200 kHz (limited use to about 1 MHz).The DDS solution gives a good sine, crystal stable frequency up to something like 10 or 40 MHz. However no triangle and limited modulation. A few DDS chips offer triangle, but with limited qualitiy and frequency (e.g. 100 kHz). A rectangle needs an extra comparator circuit.With the DDS the frequency is set digitally opposed to a potentiometer with the analog solution - it depends what is more convenient.In both cases you need an output amplifier, which is somewhat easier for the low frequency xr2206. The DDS solutions also needs the controlling µC.

author: ez24
author_rank: Super Contributor
timestamp: May 19, 2016, 11:40:06 pm
content: Quote from: Abayomi on May 19, 2016, 01:14:28 amI think this can be "build" otherwise the OP has been furnished a "circuit diagram" All bases covered.http://www.ebay.com/itm/XR2206-Function-Signal-Generator-DIY-Kit-Sine-Triangle-Square-Output-1HZ-1MHZ-/111856600454?hash=item1a0b2c4586:g:Nn4AAOSw5IJWegvj