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I am currently using a DAC (mcp4922) and want to send the output voltage (0 to 5V) to 1 of many (14) inputs on an Arduino Mega.

I am currently using some VN2222 fets for switching (because I had them laying around) but would like to get something with a higher density. They are all connected to the DAC output and switched with 14 output pins from an Arduino. I know there is a DIP 20 part with 4 fets on-board, but I would still need 4 of them to get the number of pins.

Does anyone have suggestions on other parts that would do something similar Hopefully a single DIP style case? Note that the switching is done to only one of the inputs at a time and typically for several milliseconds before it is switched to another one, so no high-speed pulsing-timing here.

Thank you!

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    \$\begingroup\$ Your question makes little sense. The DAC output is analog, but you talk about TTL level, which is digital. And what's the function of the FETs? How are they controlled? What do they switch, or amplify? \$\endgroup\$ – stevenvh Jul 23 '12 at 18:37
  • \$\begingroup\$ My mistake. The output of the DAC is actually switched into one of many Analog Inputs on the Arduino. What I need to do is inject a determined voltage into a single analog input and read it. This is done as part of a test rig and as such has litle (or no) practical use. \$\endgroup\$ – Zot Ditz Myo Jul 24 '12 at 11:05
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If understand correctly you are looking for a simple multiplexer, something like the 74HC4067 should do - it's a 1 to 16 multiplexer/demultiplexer.

mux

mux2

Simply input your signal to pin 1 (COM IN/OUT) and use S0 to S3 to switch it between I0 to I15 (each of which are connected to your Arduino inputs) For example if you want to connect to I7, then you set S3 to 0, S2 to 1, S1 to 1, S0 to 1 (i.e. 0111 binary = 7 decimal)

This is a single supply IC, so it won't work if you DAC swings below ground, in that case you will need a dual rail mux (plenty out there, e.g. 4051 is an 8ch dual rail)

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  • \$\begingroup\$ My DAC will be outputting from 0 to 5 V and from the specs, this is EXACTLY the chip I needed! As a bonus, I need only 4 pins to manage the addresses, excellent! \$\endgroup\$ – Zot Ditz Myo Jul 24 '12 at 11:10

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