Anyone have any good schematics for a function generator?

[Devius]

I'd like to build my own function generator with sine, square, and triangle waves. I would also like to include a momentary off switch to test delays, envelope filters etc. If anyone knows some good schems for this, I would be greatly appreciative if you could send it my way.

[R.G.]

There are sound card programs, even free ones, that do this, and much much more.

[samhay]

If you want to go down the DIY route, take a look at the XR-2206 chip.

[EATyourGuitar]

xr-2206 is good if you absolutely need sine wave. if not, use a 555 timer like I do. if your into sine wave generators, maybe just spend $50 and get the miniDDS. that way you can dial in exactly what frequency and amplitude you want on the digital display using the numeric keypad. having consistent repeatable functions is important for getting reliable data or good calibraton. having a 440 A test tone is good for tuning oscillators in keyboards. miniDDS FTW!

[alanlan]

Ibuilt a great little function generator once from a Practical Electronics magazine project. It was based on the 8038. I'm not sure if the schematic is around online but well worth it if you can find the article. It would have been from around 1979 to 1981 ish I think.

It had tri/sin/square outputs plus sync and a frequency range up to 100KHz.

[R.G.]

The 2206, 8038, and even better the MAX038 make great function generators. Unfortunately the MAX038, which was the best of the lot, is no longer made, and the 8028 may not be. But look for "function generator kits":

https://www.sparkfun.com/products/9002
http://www.jameco.com/1/3/function-generator-kit
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-118
http://www.circuitspecialists.com/kit-23.html
http://www.electronics-diy.com/function-generator-kit-xr2206.php
http://www.amazon.com/Same-as-FG-500-Kit-Form/dp/B0002MQEW4
http://www.kitsusa.net/phpstore/html/Elenco-FG-500K-1MHz-Function-Generator-Kit-5974.html
http://www.kitsrus.com/pdf/k101.pdf
... 720,000 results for "function generator kit"

I use a software oscilloscope, so there's always a computer going when I do bench work. A sound card output program for signals up to a couple of volts works fine for my work.

[Devius]

Thanks for the replies! I've found a decent schematic using the 8038 but it seems damn near impossible to find. I'll check out the 2206.

[Jdansti]

If this is just for diagnostic purposes, and if you have an iPhone, iPad, or iPod, there are a lot of function generator apps. Here's an example:

https://itunes.apple.com/us/app/signal-generator/id409241018?mt=8

[Skruffyhound]

I have a couple of the iPhone apps that I used before I got a function generator with my scope.

Merlin made this
http://www.diystompboxes.com/smfforum/index.php?topic=83930.msg789821#msg789821

Walt made this, damned if I can find the thread though.
http://www.aronnelson.com/gallery/main.php/v/waltk/XR2206Oscillator/

[waltk]

You can still find XR2206 chips.  The layout I made is pretty much straight from the datasheet.  If I had to do it over again, I would include 2 pots for frequency adjustment - one for coarse and one for fine.

[defaced]

Merlin made this
http://www.diystompboxes.com/smfforum/index.php?topic=83930.msg789821#msg789821

+1 to that project.  I know it doesn't have all the features you want, but a square wave can be added with the addition of a comparator chip and a triangle can be added with a single op amp stage (plenty of schematics come up when googling "triangle wave generator").  But the base project, for the cost of a quad op amp, is a very capable DIY audio generator.