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So from my understanding, an analog mux such as CD74HC4067E will be able to output diferent voltages based on its inputs.

Thus for an example if I connect 4V, 3.3V, 2.2V and 0V to a 4:1 mux with 00, 01,10,11 being the selectors for each of the above voltages respectively. What would it output if I select 10?

My understanding is that it should output 2.2V or whatever is connected to that corresponding channel. Sorry for the basic question, I just want to be sure before I buy the chip.

Sample of 4:1 Mux

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  • \$\begingroup\$ I would think so yes. Often these are used for varying waveform inputs, but a static level voltage would work fine too. \$\endgroup\$
    – KyranF
    Jun 9, 2015 at 17:27
  • \$\begingroup\$ Thanks for the quick response! Yea I just wanted to double check since I had originally bought a digital mux \$\endgroup\$
    – David
    Jun 9, 2015 at 17:35
  • \$\begingroup\$ I've made a piecemeal sinewave generator using this method. \$\endgroup\$
    – Andy aka
    Jun 9, 2015 at 17:35
  • \$\begingroup\$ Was it tasty? :P \$\endgroup\$ Jun 9, 2015 at 17:38
  • \$\begingroup\$ @VladimirCravero The "frequency" that I eat is is lower these days ;) \$\endgroup\$
    – Andy aka
    Jun 9, 2015 at 22:08

1 Answer 1

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Yes, you can do this, but there may (or may not) be a problem. You cannot use your selected voltage as a power supply. Look at figure 1 in the typical performance section. The effective resistance in the switch will be in the range of 60 to 90 ohms. And the maximum current you can pass is 20 mA.

Even at 10 ma, a resistance of 60 ohms will cause a voltage drop of .6 volts, so in your example, if the load is drawing 10 mA, the output voltage will be 1.6 volts, rather than 2.2 volts.

This may not be a problem. For instance, if you are monitoring several power supplies with a high-impedance A/D converter, input impedance better than 10 k ohm, your measurement will be accurate to ~ 1%. But if you intend to actually power a circuit, you'll need to be very careful.

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  • \$\begingroup\$ Thanks for the feedback. Yea that actually would be a problem since I do need the voltages to be accurate \$\endgroup\$
    – David
    Jun 9, 2015 at 18:43
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    \$\begingroup\$ @David - Simple enough. Just add a buffer amp after the mux. \$\endgroup\$ Jun 9, 2015 at 20:57
  • \$\begingroup\$ +1 for the buffer. My first experience in analog muxes was to read a bunch of manually-operated potentiometers, and I naively connected all the pots directly across the supply, the wipers directly to the muxes, and the muxes directly to the ADC inputs of my uC. Several months later, being on and cycling 24/7, they stopped being accurate anymore. The replacement had a resistor in series with each mux's common pin, that then fed a rail-to-rail buffer amp. \$\endgroup\$
    – AaronD
    Jun 10, 2015 at 22:23

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