Available cheap ICs/modules for a DIY function generator

[Dhanushka]

I am going to design a function generator (at least 20MHz) with a cheap(less than 15$) ICs/modules. What are the available suitable cheap ICs/modules on ebay according to your experiences and knowledge?

I expect a simple list of available both analog type(MAX038, XR2206 etc.) and DDS type (AD9834, AD9850 etc.)

Thank you.   

[ebclr]

https://pt.aliexpress.com/item/Gerador-de-Sinal-ICL8038-Kit-DIY-Tri-ngulo-Sine-Pra-a-Sawtooth-5-Sa-da-Hz/32899062780.html?spm=a2g03.search0104.3.51.6a147610FS3Wcz&transAbTest=ae803_3&ws_ab_test=searchweb0_0%2Csearchweb201602_8_10065_10068_10547_319_10059_10884_317_10548_10887_10696_321_322_10084_453_10083_454_10103_10618_10307_537_536%2Csearchweb201603_16%2CppcSwitch_0&algo_pvid=d606b782-4a1d-40dd-8843-f5e0508b63ea&algo_expid=d606b782-4a1d-40dd-8843-f5e0508b63ea-7

[coromonadalix]

a 20mhz generator would be a max038   and dds related boards

xr2206 goes up to 1mhz

You have already made cheap dds generators and boards on many websites, why taking the hard route

[Kleinstein]

Even the max038 is hard pressed at 20 MHz. Anyway this chips is unobtainable (stopped production some 20 years ago) and if one gets an offer for cheap - chances are high it's fake.

The AD9850 modules may work though some boards have questionable quality with the filter. A don't think the AD9834 would go to 20 MHz output - the DSS chips often show the DDS clock and the practical may output is more like 1/3 the DDS clock - though the DS often show 1/2.5, which would need a rather good filter.

There is also the way of the cheap chinese generators: a FPGA or µC and R2R resistor chain as a cheap, though poor quality DAC.

[coromonadalix]

I have 2x Max038 in stock, never used loll   there was a time you could get 2 samples of many ic's at Maxim

[bloguetronica]

...
The AD9850 modules may work though some boards have questionable quality with the filter. A don't think the AD9834 would go to 20 MHz output - the DSS chips often show the DDS clock and the practical may output is more like 1/3 the DDS clock - though the DS often show 1/2.5, which would need a rather good filter.
...

You can push the AD9834 to produce a 20MHz sinewave, provided that you have the B version, a nice 80MHz oscillator for the DDS clock and a good and well tuned reconstruction filter. However, mind that the amplitude will be fairly reduced.

A good design with the AD9834 can go up to 8MHz when producing sinusoidal signals, or up to 2MHz for the triangular wave. If you need to produce signal having higher frequencies, you should choose the AD9102 or better.

Kind regards, Samuel Lourenço

[wilfred]

a 20mhz generator would be a max038   and dds related boards

xr2206 goes up to 1mhz

You have already made cheap dds generators and boards on many websites, why taking the hard route

I wish Dave would do a blog on the futility of DIY and hobby interest in electronics these days with so much already available far cheaper than you could make it yourself. One of the big advantages of Electronics Magazine projects was that you could make some thing cheaper and maybe better than a commercial design. No wonder it is dying out if the number of such comments I have been reading here lately is a reliable guide.

The only thing that gives me pause to have doubts is that it is said only when someone suggests they want to do it for some unknown reason.

I picked up a couple of MAX038 a while back for A$3 and hatched another dream of some project which may, but probably won't, see the light of day. I was going to make Dave's function generator design. You can't get the output buffer chip he used and I have to source another and then see if I can figure out how to adapt the design and maybe learn Kicad  so I can make  a PCB. Then make the PCB  and solder it up and probably debug it. Honestly, what an idiot, why would I bother? I've already got so many other projects I'm also not working on and probably shouldn't  bother with either.

I also wish I hadn't bought some of the parts to make the EMC probes Dave built. Luckily I saw the comments that you could buy them so cheap before I wasted time on them.
Unfortunately I realised too late when Dave said any modern DSO should be OK he wasn't saying Dick Smith Oscilloscope^*. My 10MHz single channel one isn't the DSO he had in mind.

(*) - Yes I am well aware that no Dick Smith Oscilloscope was ever modern.

[Simon]

It's horses for courses. i need several PWM generators with 24V output. You can't even buy them and if you could it would be prohibitively expensive to buy a function gen just for one waveform.

[Zero999]

https://www.amazon.co.uk/HiLetgo%C2%AE-AD9850-Generator-0-40MHz-Equipment/dp/B0795DQ6M6?source=ps-sl-shoppingads-lpcontext&psc=1?source=ps-sl-shoppingads-lpcontext&psc=1

[EEVblog]

Unfortunately I realised too late when Dave said any modern DSO should be OK he wasn't saying Dick Smith Oscilloscope^*. My 10MHz single channel one isn't the DSO he had in mind.
(*) - Yes I am well aware that no Dick Smith Oscilloscope was ever modern.

Your Dick Smith scope isn't even a DSO, it's an analog CRO, no digital doodad.

[wilfred]

Unfortunately I realised too late when Dave said any modern DSO should be OK he wasn't saying Dick Smith Oscilloscope^*. My 10MHz single channel one isn't the DSO he had in mind.
(*) - Yes I am well aware that no Dick Smith Oscilloscope was ever modern.

Your Dick Smith scope isn't even a DSO, it's an analog CRO, no digital doodad.

I really was just making a self deprecating joke. I am frustrated by people who keep telling others to buy a pre-built module or commercial product. It's like letting someone just sit down and enjoy the act of creation or discovery has gone out of fashion. Even if someone wants to build a retro computer with a Z80 or some other ancient CPU will surely get comments saying a laptop  with an i7 is faster.

What is the point of a hobby if it isn't to find out what you can do, make, create, learn and share with others?

[Simon]

measuring instruments and other devices that are required to be accurate are a bit pointless making yourself. But lots of stuff that just needs to work can be home made.

[mikerj]

measuring instruments and other devices that are required to be accurate are a bit pointless making yourself. But lots of stuff that just needs to work can be home made.

Making your own test/measurement kit used to be a staple of hobby electronics.

[Simon]

Yes, but the sort of accuracy we take for granted now is not what "we used to" have. Power supplies yes up to a certain power. Various gadgets sure but you can't compete with off the shelf multimeters and oscilloscopes, best buy goods ones and use them to develop what you wanted to develop.

[Zero999]

It can be done with a triangle wave generator and a wave shaper circuit.
https://www.eevblog.com/forum/beginners/simple-analog-function-generator-design/