Function generator ICs

[bearman]

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

[Bored@Work]

What changed in the industry that these are all retired

DDS happened (and that AFAIK a fab burned down where the x38 were made).

Check Analog Devices for DDS chips.

[Zero999]

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.pdf
http://www.analogzone.com/den7.pdf
http://www.kelm.ftn.uns.ac.rs/literatura/mi/pdf/Wave-Shaping.pdf
http://www.ece.stevens-tech.edu/~bmcnair/EE359-F09/lecture15B.pdf
http://www.intersil.com/data/fn/fn957.pdf

[alm]

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.

[bilko]

Check the data sheet for LM13600, parts available most places, ebay at just above 1$ per part

[Bored@Work]

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.

They had RoHS compliant versions, e.g the MAX038CPP. You can still find that version on eBay.

[grenert]

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

[bearman]

THANX ALL

Well 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

[bilko]

For music generation see CEM3396, used in a lot of early synths and still available on ebay http://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

[Conrad Hoffman]

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!

[Bored@Work]

I agree that the DDS chips are the bomb today and any sane person would use them. I still like analog

But 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.

[Zad]

Analog are pretty much the only people who do DDS
http://www.analog.com/en/rfif-components/direct-digital-synthesis-dds/products/index.html

If 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!

[bearman]

Thanx everyone.  Time to do some home work.

Happy Soldering all.



B

[Jakey]

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!

[Cliff Matthews]

* Reply #2 - Updated URL: AN-263 Sine Wave Generation Techniques

[Cliff Matthews]

Anyone interested in developing a PSoC based functional equivalent of those VCOs? PSoC PWM module has a LED dimming mode, which is basically a sigma delta modulator. That can be coupled with analog MUX and VDAC to form a true analog volume control, then the output signal goes to CT module to get LPFed, then buffered by OPAMP module.

Would this be 5LP compatible? If so, yes.

[Cliff Matthews]

My youngest son through 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 ;-)

[David Hess]

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.

[ali_asadzadeh]

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

[Jakey]

* Reply #2 - Updated URL: AN-263 Sine Wave Generation Techniques

Beside 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).

[Cliff Matthews]

* Reply #2 - Updated URL: AN-263 Sine Wave Generation Techniques

Beside 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).

W2AEW 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.

[theHWcave]

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.

[Cliff Matthews]

..the clones can't go much above 12V.

Waveform 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..) 

[Kleinstein]

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.

[David Hess]

W2AEW 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.

Using 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.