I am learning electronics so this is a beginners question. Its about the CD4066 IC as mentioned here


Is the 4066 equivalent to four independently controllable relays, where one relay switches on the pair X1,Y1?-Is this the purpose of this IC? So four relays are required to switch (the 4 pairs of audio signals) X1,Y1




Because in the IC there are four switches that can control the four pairs above. So with this IC 4 speakers are controllable by a digital CPU.

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    \$\begingroup\$ look at how much current & voltage you can switch - very limited. The chip is not equivalent to 4 relays. \$\endgroup\$ – JIm Dearden Jan 3 '17 at 13:18
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    \$\begingroup\$ Related: electronics.stackexchange.com/questions/32413/…. CD4066 can be used for audio, but the limitations (explained by Andy below) make it a bit difficult to work with. In particular, you have to ensure your signal is within the bounds of the CD4066 supply rails, which means either shifting the signal or having the audio ground inbetween the CD4066 supply rails. \$\endgroup\$ – dim lost faith in SE Jan 3 '17 at 13:31
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    \$\begingroup\$ Just one warning: there is no way you can switch the speaker signals with CD4066. If you want to use it to change your audio source, you should use the CD4066 before the amp and switch the input signal (which is low current). \$\endgroup\$ – dim lost faith in SE Jan 3 '17 at 13:37
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    \$\begingroup\$ You might be able to control headphone signals and you can certainly control line level audio signals, but definitely not speaker signals. \$\endgroup\$ – Brian Drummond Jan 3 '17 at 13:41
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    \$\begingroup\$ @Pete Yes, but I doubt the speaker signals are less than 10mA. In a typical 8ohm speaker, it means 0.8 milliWatts of power. Or maybe you like very very very quiet music. If you really want to switch speaker signals, use relays. \$\endgroup\$ – dim lost faith in SE Jan 3 '17 at 13:45

You can regard the 4066 as 4 relay contacts but there are a bunch of constraints that limit this analogy. The main ones are: -

  • On resistance is massively higher than a relay contact (typically 125 ohm)
  • Ohmic linearity with input signal voltage means signal distortion may occur (unlike normal relay contacts).
  • Any input / output signal must be constrained to the power rails of the device. In other words, there is *some" isolation capability that is useful but don't expect truly AC signals to do anything other than either badly distort or burn the chip.
  • Maximum current is limited to a few mA
  • Open circuit capacitance is quite high thus limiting the ability to "open-circuit" high speed signals.
  • \$\begingroup\$ So what the main purpose of this 4066 IC? Can it control 4 audio speakers with a CPU? \$\endgroup\$ – Pete Jan 3 '17 at 13:26
  • \$\begingroup\$ Main purpose is for switching low level analogue signals and, under all but the very lowest power applications, it cannot switch speaker signals (apart from the fact that speaker signals are AC as mentioned and this is a problem). \$\endgroup\$ – Andy aka Jan 3 '17 at 13:27
  • \$\begingroup\$ do you mean low voltage and power when you say " low level analogue signals" \$\endgroup\$ – Pete Jan 3 '17 at 13:29
  • \$\begingroup\$ Any signals are basically constrained to be within the power rails so, if your power rails are 0 V and 5 volts then signals have to wholly be constrained within these limits with zero exceptions. Given the peak current is about 10 mA this means low power to me (125 ohms on resistance) but can also be low voltage or anything up to (say) 5 Vp-p. \$\endgroup\$ – Andy aka Jan 3 '17 at 13:34
  • \$\begingroup\$ Using the relay analogy- considering one pair x1,y1-when there is no signal to turn on the transmission gate-does this mean the resistance is zero between x1,y1? \$\endgroup\$ – Pete Jan 3 '17 at 13:44

These are not four relays but transmission gates.

The circuit (taken from here) looks like this enter image description here

As you can see the switch itself consists of two MOS transistors.

For details about the switching capabilities have a look at the datasheet.

  • \$\begingroup\$ So what the main purpose of this 4066 IC? Can it control 4 audio speakers with a CPU? \$\endgroup\$ – Pete Jan 3 '17 at 13:26

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