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I'm relatively new to electronics and have never used a DAC before. I have a DAC0800 and a LF351N op-amp and have tried to set them up so that I can have a voltage output determined by the 8 digital inputs to the DAC.

My plan is to eventually connect the DAC inputs to the outputs of an EEPROM chip. The analog output of the DAC will then connect to the control pin of a 555 timer, to change its frequency.

To power it, I am using four 1.5V AA batteries in series to give 6V.

I was wondering whether anyone has any experience with this chip or circuit diagrams that could help me figure it out? It's the power that's the issue - the examples I can find usually use a dual rail supply of more than 6V, but I'd like to avoid that if possible. Alternatively, is there an easier way of producing a square wave of digitally-controlled frequency, than using a DAC connected to a 555 timer?

Thank you!

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  • \$\begingroup\$ "is there an easier way of producing a square wave of digitally-controlled frequency, than using a DAC connected to a 555 timer?"- what do you need this variable frequency square wave for, and what will be controlling it? \$\endgroup\$
    – Bruce Abbott
    Dec 28, 2020 at 22:45
  • \$\begingroup\$ The signal will be connected to a speaker (through a capacitor) to produce different notes, so the frequency does not have to be exact. An EEPROM chip with an 8-bit output and address lines connected to a binary counter controls it. \$\endgroup\$
    – user117279
    Dec 28, 2020 at 22:54
  • \$\begingroup\$ Nice project, but it is very old-school and can be replaced by an MCU with built-in DAC and it will be more versatile. But it is easier, if not easiest way to do what you want, play tones with digitally controlled frequency, usually hardware timers can control DMA playback of PCM samples to a 12-bit DAC. You get even two channels stereo, and perhaps a megabyte of sample memory, and expandable via USB or SD memory cards. \$\endgroup\$
    – Justme
    Dec 28, 2020 at 23:18
  • \$\begingroup\$ Thanks for the advice, I usually use microcontrollers but I wanted to try doing a project without one for a change to learn more about electronics, which is the reason for the old-school tech. It won't be very practically useful but I've had fun designing it. \$\endgroup\$
    – user117279
    Dec 28, 2020 at 23:27
  • \$\begingroup\$ For hobbyists, I usually recommend a cheapy MCP4725 module, (12 bit DAC with EEPROM). Feel free to ask @tlfong01 for more follow up newbie questions. \$\endgroup\$
    – tlfong01
    Dec 29, 2020 at 1:42

1 Answer 1

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The fact that the DAC0800 specifies needing at least +/- 4.5V means that you will not be able to run this chip with a 6V source (at least not to spec). You can DC bias this part to "fake" a bipolar supply but you will need at least a 9V supply to have the headroom to swing.

If possible, try to stick to any of the manufacturer's reference designs as much as as you can (Figures 18 and on). These can be a good starting point for most designs.

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