Function generator ICs - Page 1
Forum section: electronics / projects

author: bearman
author_rank: Regular Contributor
timestamp: October 06, 2011, 08:24:34 pm
content: Hey folks. I am looking for a waveform/function gen IC. The ICL80938, MAX038, XR2206 and NTE864 all seem to have been retired. If you can find one they are selling for more than gold prices these days. I saw an ICL8038 for $50.00 USD on ebay.Anybody have any suggestions on newer ICs out there that perform these classic functions.I need a VCO capability with sine wave output in audio range only.What changed in the industry that these are all retired??Thanx all.B

author: Bored@Work
author_rank: Super Contributor
timestamp: October 06, 2011, 09:05:45 pm
content: Quote from: bearman on October 06, 2011, 08:24:34 pmDDS happened (and that AFAIK a fab burned down where the x38 were made).Check Analog Devices for DDS chips.

author: Zero999
author_rank: Super Contributor
timestamp: October 06, 2011, 09:10:26 pm
content: I'd probably go for a triangle wave generator made with the LM339 (see the datasheet which can be foun on Google) and a sine wave shaper, see attached.Here's some more reading:http://www.national.com/an/AN/AN-263.pdfhttp://www.analogzone.com/den7.pdfhttp://www.kelm.ftn.uns.ac.rs/literatura/mi/pdf/Wave-Shaping.pdfhttp://www.ece.stevens-tech.edu/~bmcnair/EE359-F09/lecture15B.pdfhttp://www.intersil.com/data/fn/fn957.pdf

author: Unknown
author_rank: Unknown
timestamp: October 06, 2011, 09:40:19 pm
content: I think the issue with the MAX038 was that there wasn't enough demand for Maxim to make it RoHS compliant, so they discontinued it.DDS would probably also be my choice if you want a fairly pure, stable sine.

author: bilko
author_rank: Frequent Contributor
timestamp: October 06, 2011, 10:52:52 pm
content: Check the data sheet for LM13600, parts available most places, ebay at just above 1$ per part

author: Bored@Work
author_rank: Super Contributor
timestamp: October 06, 2011, 11:20:12 pm
content: Quote from: alm on October 06, 2011, 09:40:19 pmThey had RoHS compliant versions, e.g the MAX038CPP. You can still find that version on eBay.

author: grenert
author_rank: Frequent Contributor
timestamp: October 07, 2011, 12:27:01 am
content: Jameco carries both the XR-2206 chip (for $6.49) and a function generator kit that is based on that chip:http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&freeText=xr-2206&search_type=jamecoall

author: bearman
author_rank: Regular Contributor
timestamp: October 09, 2011, 11:25:10 pm
content: THANX ALLWell I guess I will have to read up on DDS.I ran across an AD9835. It is around $15 USD. I guess $6.50 USD for an XR2206 doesn't sound so expensive now.What are some DDS chips that are bread and butter availablity ICs like the old 555? I can look them up and read up on them then.I want to control frequency with a micro for musical note generation. I didn't want to use square waves for the output directly from a micro. I didn't want to have to build code to synthisize sine waves either. I want to drive a standard speaker and sine waves sound warmer than square waves.Do you have to program DDS chips with ALL your desired wave forms or do they come with some canned standard wave shapes already?B

author: bilko
author_rank: Frequent Contributor
timestamp: October 10, 2011, 09:47:49 am
content: For music generation see CEM3396, used in a lot of early synths and still available on ebayhttp://www.google.co.uk/url?sa=t&source=web&cd=1&sqi=2&ved=0CCIQFjAA&url=http%3A%2F%2Fwww.synthtech.com%2Fcem%2Fc3396pdf.pdf&rct=j&q=cem3396&ei=S76STuyMH4uLhQfu-PzoDw&usg=AFQjCNFKcZjiDjMnzS93rVhQZSTZWPGMqA&cad=rja

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: October 11, 2011, 04:33:41 am
content: The expensive 8038s on eBay are the ceramic and mil spec ones. The rest are in the $10 range. Those were always a bit more expensive than other solutions, but you could do sweep generators and all sorts of things easily. For an audio person like me the downside was always that little peak on the top and bottom of the waveform. Remember the Southwest Technical Products Co. (SWTPC) 8038-based function generator? It was the first decent function generator the hobbyist could afford. I agree that the DDS chips are the bomb today and any sane person would use them. I still like analog and don't forget you can build a really nice ramp/triangle generator out of a good FET opamp and a comparator, then do a diode or other rounding circuit to make the sine wave. You can build a function generator for $1 out of the junkbox, or spend whatever you want. For synthesizer purposes you can also make a variable slew rate limiter, feed it a square wave, and control the slope to make it sound any way you want!

author: Bored@Work
author_rank: Super Contributor
timestamp: October 11, 2011, 04:50:09 pm
content: Quote from: Conrad Hoffman on October 11, 2011, 04:33:41 amBut DDS doesn't deprive you of your analog experience. There is plenty to do in building a good analog output stage for the output of the DDS chip. If you look at the different DIY DDS function generators around you find that most of them suck in that department.

author: Zad
author_rank: Super Contributor
timestamp: October 12, 2011, 01:58:04 am
content: Analog are pretty much the only people who do DDShttp://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/products/index.htmlIf you only need audio frequencies, then you can use an embedded micro to simulate DDS. Either way, there is still plenty to do in the analogue electronics!

author: bearman
author_rank: Regular Contributor
timestamp: October 13, 2011, 08:34:50 pm
content: Thanx everyone. Time to do some home work.Happy Soldering all.B

author: Jakey
author_rank: Newbie
timestamp: March 25, 2018, 11:47:27 pm
content: Since this topic is superold (7 years), I'd like to re-open it again, since I'm into exactly same problem:Is there anything new, that could be replaced with ICL80938, MAX038, XR2206 and NTE864, etc. chips?Something that needs only a handful of passives and semiconductors would be perfect, without using a uprocessor.Thanks all!

author: Cliff Matthews
author_rank: Unknown
timestamp: March 26, 2018, 12:04:36 am
content: * Reply #2 - Updated URL:AN-263 Sine Wave Generation Techniques

author: Cliff Matthews
author_rank: Unknown
timestamp: March 26, 2018, 01:13:32 am
content: Quote from: blueskull on March 26, 2018, 12:48:31 amWould this be 5LP compatible? If so, yes.

author: Cliff Matthews
author_rank: Unknown
timestamp: March 26, 2018, 01:37:50 am
content: My youngest sonthrough in the towel on two USB modules(-059 suffix) I got him from Digikey. He said they were fun.. but he went back to the video games (as so many teenages). So yeah, I'd like to show him what old Dad can do with his leftovers ;-)

author: David Hess
author_rank: Super Contributor
timestamp: March 26, 2018, 04:51:33 am
content: A discrete design is not difficult but audio applications usually want a logarithmic response complicating things.An alternative design for sine wave audio applications is to generate a square wave to clock a switched capacitor filter while digitally dividing the same square wave by 100 with a pair of decade counters to provide the analog input to the same filter.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: March 26, 2018, 05:35:14 am
content: If you want to make audio, why not use an audio codec, parts like CS4344-CZZ are super cheap and would make a lot more sense for generating audio tones!!! use a STM32 MCU and a cheap SD card, that's all you need

author: Jakey
author_rank: Newbie
timestamp: March 26, 2018, 11:57:42 am
content: Quote from: Cliff Matthews on March 26, 2018, 12:04:36 amBeside this reply, I haven't got any useful info.I'm actually searching an independent IC, which can create (at least) sine, square and triangle wave, be adjustable (preferably with potentiometers, but digital inputs also accepted), frequency up to at least 300 kHz, duty cycle set at least between 5% and 95% and low distortion sine wave.Preferably also bipolar and adjustable power supply (proportional to the output level).

author: Cliff Matthews
author_rank: Unknown
timestamp: March 26, 2018, 01:36:43 pm
content: Quote from: Jakey on March 26, 2018, 11:57:42 amW2AEW has an easy square/triangle wave-shaper circuit where you could add output filters to get a sine wave. I'm not sure about getting it to 300khz though.. If you need bi-polar, you can level-shift unipolar to bipolar on the output opamp.

author: theHWcave
author_rank: Regular Contributor
timestamp: March 29, 2018, 02:25:37 pm
content: You can still buy XR2206 chips in form of kits for function generators from China. Banggood sells a kit for £4.68 at the moment. Just search for "Function generator kit". The trouble is that the XR2206 chips in these kits are very likely clones. I think the main difference is the supply voltage range. The original chip is specified for 10 to 26V and I believe the clones can't go much above 12V. The question is if there are other functions (like AM/FM or FSK) that the clones did not implement right and which go unnoticed in these kits because they don't use anything else than generating plain sine, triangle and square waveforms.

author: Cliff Matthews
author_rank: Unknown
timestamp: March 29, 2018, 03:10:08 pm
content: Quote from: theHWcave on March 29, 2018, 02:25:37 pmWaveform jitter starts at 12.0v with the fakes, see solutions here:(funny how phrases like Dave's "tongue at the right angle" has made it to even the Germans..)

author: Kleinstein
author_rank: Super Contributor
timestamp: March 29, 2018, 04:00:32 pm
content: AFAIK there are no more active analog function generator chips except maybe the XR2206 clones. With a reasonable data-sheet and source other than the kits, might be an option. The ICL8038, real XR2206 and the max038 got rare and difficult to impossible to get. If it needs to be analog, it would be down to more basic parts like OPs, comparator and so on.The modern way is going DDS, either with a dedicated chip (e.g. AD9850, AD9835,...), a FPGA + DAC or maybe a µC and DAC for the lower frequencies. However this is digital control and thus usually a µC for control.

author: David Hess
author_rank: Super Contributor
timestamp: March 30, 2018, 03:51:11 pm
content: Quote from: Cliff Matthews on March 26, 2018, 01:36:43 pmUsing a diode bridge to switch currents into a capacitor as W2AEW shows is one of the higher performance options and suitable for operation up to at least 40MHz so 300kHz is not a problem and it used to be the go-to function generator topology. Using currents and an integration capacitor avoids bandwidth limitations of an operational integrator. The low capacitance of the diodes lowers the amount of charge from switching coupled into the integration capacitor making compensation of this error more effective. Both contribute to good control of the triangle wave height which is required for low distortion sine shaping.

author: Zero999
author_rank: Super Contributor
timestamp: March 30, 2018, 10:25:32 pm
content: Quote from: David Hess on March 30, 2018, 03:51:11 pmInteresting. I've built the integrator triangle wave generator before and have found the the jellybean LM393 comparator's propagation delay seemed to be more of a limiting factor, than the integrator.The main downside I can see with the current source/sink solution is, if 50% duty cycle is required, getting the currents to match accurately could be challenging.

author: calexanian
author_rank: Super Contributor
timestamp: March 30, 2018, 11:15:54 pm
content: Jameco shows 1339 of them in stock. Interestingly enough I think that may be the last place i bought them in anger perhaps 15 years ago. I remember getting tubes from digikey and they were like .45 each. I also recall that many hundreds of thousands of them in SIOC were packaged and floating about out there when they were discontinued.

author: nuno
author_rank: Frequent Contributor
timestamp: March 31, 2018, 12:01:46 am
content: When I started exploring PSoC4 I played a bit with generating a triangle wave. Made a concept for an "analog" triangle wave generator without any CPU intervention, and didn't develop the thing further. TimClock controls the frequency, and amplitude is dependent on frequency (probing the capacitor with the scope's probe affects the frequency slightly due to probe capacitance).

author: David Hess
author_rank: Super Contributor
timestamp: March 31, 2018, 03:23:47 am
content: Quote from: Hero999 on March 30, 2018, 10:25:32 pmThe delay through the comparator is a major factor. Not only does it create a linearity error in the frequency, but it increases the amplitude of triangle wave at higher frequencies because switching happens late and the variation in amplitude increases distortion through the sine shaper. The delay can be compensated by using a capacitor to create a high pass function between the triangle wave output and comparator so that as the frequency is increased, the comparator switches earlier.QuoteIn practice the current source and sink are controlled by operational amplifiers making it easy to adjust and balance the symmetry. At least a 1000:1 control range is feasible yielding 20kHz to 20Hz.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2018, 08:55:15 am
content: Here's another thread which may be helpful.https://www.eevblog.com/forum/beginners/simple-analog-function-generator-design/msg1174548/#msg1174548I've built one of these circuits before, but don't think I got round to posting any oscillograms. If I can find one, I'll 'scope it any post the results.

author: Atom
author_rank: Regular Contributor
timestamp: March 31, 2018, 09:44:48 am
content: If you want a cheap funztion generator you can use an AD9833 it goes on aliexpress for 2.50 dollars but you need a microcontroller to instructions to it,It can go up to 10Mhz ...here it is someaone that has already done it if you want here's the linkhttp://www.vwlowen.co.uk/arduino/AD9833-waveform-generator/AD9833-waveform-generator.htmI've ordered 2 of those right now, planning onto doing a 2 channel waweform generator

author: MarkF
author_rank: Super Contributor
timestamp: March 31, 2018, 06:35:32 pm
content: Quote from: Atom on March 31, 2018, 09:44:48 amI actually like the AD9834 better. It gives you the ability to adjust the output level directly on the chip. Here is the design I've done which will give you 1Hz to 4MHz at 3Vpp output. I'm currently adjusting the gains and DC offset voltages to the output voltage. This chip provides sine and triangle outputs and a square wave using the signBit output. The signBit output is connected to a MCU output to also provide a sync when generating frequency sweeps.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 31, 2018, 06:56:27 pm
content: AFAIK the high performance max038 got obsolete quite abrupt because the process used to make it was no longer available to Maxim.These DDS chips / modules replaced the FGen chips in quite some applications. DDS is probably one reason you don't get those chips anymore.The rectangular signal directly from the DSS highest bit / sign is usually poor quality with quite some jitter. To get a good quality rectangle it needs the reconstruction filter followed by a comparator.However showing DDS generators is kind of off topic here. A relatively simple analog replacement circuit might be an option today. However the option for amplitude modulation in the XR2206 is kind of a little difficult. The sine shapers might turn out to be temperature sensitive. Otherwise the analog circuit is not that difficult.

author: Atom
author_rank: Regular Contributor
timestamp: April 01, 2018, 08:35:08 am
content: Quote from: MarkF on March 31, 2018, 06:35:32 pmOh i didn't know that, by the way , why areyou limiting the frequency at 4mhz when it can go up to 75mhz ? It's because you don't need those high freuencies?

author: MarkF
author_rank: Super Contributor
timestamp: April 01, 2018, 08:51:12 am
content: Quote from: Atom on April 01, 2018, 08:35:08 amSee attached app note.Because I'm only using a 32.768 MHz clock. A power of 2.