Function Generator chips

Discussion in 'General Electronics Chat' started by Danm1, Oct 26, 2013.

  1. Danm1

    Thread Starter Member

    Jul 19, 2010
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    Can someone suggest any function generator chips that I might use in a new design? I need a variable frequency sine wave from DC up to >100k Hz or maybe >10M Hz. I'm currently looking at the line of DDS parts from Analog Devices, which look good, but if there is some other family of parts then I'd like to look at them.

    Thanks,
    Dan
     
  2. ajm113

    Member

    Feb 19, 2011
    176
    5
    Well... There are always micro-controllers and shift registers. :) Plus creating a digital interface would make it easier, but it doesn't matter if you go for the analog approach too using some pots. ;) If your using SMD get a nice 32bit microcontroller. You can get up to 100 I/O pins and very fast speeds. (Woowie) or get a good 20-40hz 8-16bit chip thats DIP package for through hole. Atmel has more of a range of speeds for DIP packages as I can tell.
     
  3. adam555

    Active Member

    Aug 17, 2013
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    I just used an ICL8038 in a function generator project: 3 simultaneous wave forms, variable frequency up to 300 KHz, easy to set up, and just $1 on ebay including P&P. Probably not the best, but no other option was anywhere near in terms of price/options/simplicity.
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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  5. Danm1

    Thread Starter Member

    Jul 19, 2010
    55
    7
    Thanks for the good suggestions. I'd like to minimize the component count somewhat, to reduce my chance of a mistake on my part.

    Another feature that would be nice to have is a way to adjust the amplitude, some of the ADI parts have this, such as the AD9834. Otherwise I may need to have a variable gain amplifier after the generator.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    With something like an STM32 MCU you can create an arbitrary waveform generator all with one chip.
     
  7. TorontoBob

    New Member

    Oct 5, 2013
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    And if you wanted to go up to 20MHz there is the MAX038 by Maxim. Datasheet is available at their website http://datasheets.maximintegrated.com/en/ds/MAX038.pdf
    with an application note on how to use it at
    http://www.labc.usb.ve/paginas/gfernandez/Ec_3881/pdf/Waveform_Generators/Maxim/AN650.pdf
     
  8. Danm1

    Thread Starter Member

    Jul 19, 2010
    55
    7
    One other issue I need to have a better handle on in this function generator is the resolution of the counter. In many generators, there is a counter that the output goes to a ROM lookup table to create a sinusoid(I just need a sine wave, no square or triangles) So some of the ADI parts have a 10 bit counter, others have a 12, 14 or 16 bit counter. The down side to a 16 bit counter is that you need an internal clock that is fast enough to get thru all 64k states for every cycle of the output wave form.

    So the big question is: will a 10 bit counter be good enough or with I get noticeable noise due to the stair step shape of the resulting waveform?
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    They do not make that chip anymore. In fact they make very few analog frequency generator chips (sine wave). They have been replaced by the direct digital synthesis (DDS). On ebay they sell a lot of ready made DDS modules quite cheap.
     
  10. Danm1

    Thread Starter Member

    Jul 19, 2010
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    7
    yeah t06afre is right, the DDS modules(mostly from China) are cheap, some of which are less expensive than the individual chips are. I'm probably using a couple of these for my prototype.
     
  11. Gibson486

    Member

    Jul 20, 2012
    199
    12
    As someone said, they do not make those sine wave chips any more because they are replaced with DDs chips. The biggest issues I found with these chips are that they have small output ranges. Last I looked, I could only get a 1V pk to pk, if that. Yes, you could put gain stages bring it up, but when you go up in frequency, it gets tougher.

    The closest thing I know is the XR2209. The only issue is that it only outputs a triangle and square wave. If you know your analog, you can easily make it a sine wave, however.
     
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