function generator

[dorin.iordache]

Hi guys! I am looking to build my first function generator based on xr2206 or icl8038 . The problem is that the amplitude of the generated signal varies a lot from square to sine and so on. Therefore i am wondering if any of you guys have a good working project documentation for a function generator with an amplitude of the output around 10V pk-pk and to generate from 1 Hz to a few hundred kHz or even few Mhz. Thanks guys!

[dannyf]

from 1 Hz to a few hundred kHz or even few Mhz.

Set a realistic goal and you are half way to success.

[dorin.iordache]

I said that because I want to be open to various range of schematics. Anyway I found this circuit diagram http://electronics-diy.com/function-generator-xr2206.php . Now i was thinking about using some operational amplifiers on the triangle/sine output stage in order to amplify the signal and get the desired output amplitude. I should use an op amp with a large slew rate value and that can cope with the high frequency. A gain of 3-4 should do the job therefore 1+ (Rf/R1) should give me the desired gain. Am i on the right track ? Any suggestions or maybe already designed circuit diagrams?

[bance]

You could try Dick Cappels version.....

http://www.cappels.org/dproj/functsweep/functionswp.html

[dorin.iordache]

I've decided to build the project found here http://mdiy.pl/generator-funkcyjny-400khz-na-icl8038/?lang=en . It has all i need and from what i can see it works good enough. Also it has all the PCB files so I won't have to do those by myself. As a frequency counter i haven't decided it if i should go for the Attiny2313 or PIC16F84. I already have a pickit2 so i might go for the pic in the end. I will start the building process sometimes next week when my parts will arive. Also my oscilloscope should arrive by then too so I will be able to measure the performance of the function generator.

[Rerouter]

both should work well, as they both have enough timer hardware to do a nice reciprocal count up to a few Khz, from then on you can switch to fixed time base counting,

 

[mrkev]

Just btw, were those chips discontinued? I had planned project to rebuild my old generator with xr2206 but I never did it because I couldn't find any suplier that would sold those chips anymore.

[casinada]

http://www.taydaelectronics.com/ic-integrated-circuits/specialized-function/xr-2206-xr2206cp-xr2206-monolithic-function-generator-ic.html
 

[Simon]

Just btw, were those chips discontinued? I had planned project to rebuild my old generator with xr2206 but I never did it because I couldn't find any suplier that would sold those chips anymore.

http://www.ebay.co.uk/itm/SparkyLabs-ICL3086-function-generator-IC-sqaure-sine-triangle-smultaneously-/171480639372?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item27ed0ae78c

Not made by the original manufacturer but they are easy to make these days and someone took the trouble to make an equivalent.

[rdl]

What is different about an ICL3086 compared to the XR2206 and ICL/MAX8038? Google seems to think you're about the only place in the world to get an ICL3086.

[dorin.iordache]

well...I got the ICL8038 from ebay for £2.48. I bought the PIC16F84 and the Attiny2313 to give them a try.Even if i'm not gonna use one of them in the frequency counter i can always use it for something else.

[mrkev]

Just btw, were those chips discontinued? I had planned project to rebuild my old generator with xr2206 but I never did it because I couldn't find any suplier that would sold those chips anymore.

http://www.ebay.co.uk/itm/SparkyLabs-ICL3086-function-generator-IC-sqaure-sine-triangle-smultaneously-/171480639372?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item27ed0ae78c

Not made by the original manufacturer but they are easy to make these days and someone took the trouble to make an equivalent.

Yes, I've seen a lot of those, but I'm never confident using chips like that in designs. You never know if you'll be able to get more when you need replacement, f.e. two years later...  Those XR2206 were great, often used by amateurs in sound effects (because you could easily generate variety of waveforms).

Do you have at least some datasheet, I couldn't find anything... Or are they just with identical pinout and ratings? Chips like that are often made by some lo-end manufacturer, so are they even reliable?

[rdl]

The thing is, the chip I was questioning is the ICL3086. That number, 3086, does not resemble any of the others and I did not find much info about it using Google, other than it's sold by Sparky Labs.


edit: and yes, I meant MAX038, I was thinking it used the same number as the ICL8038. I always thought the Maxim version was just an improvement of the old ICL chip, but I've never used either so I'm probably wrong.

[Rerouter]

as your already using a micro, you could always just use a AD9850 module, that will get you from 0.02Hz to a few 10's of Mhz, with sine and square, all you have to do it amplify it to 10V peak to peak with an op amp