Analog switches

Discussion in 'General Electronics Chat' started by Envergure, Mar 16, 2010.

  1. Envergure

    Thread Starter Member

    Jan 14, 2010
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    Hi, I'm wondering what I can use as a voltage-controlled four-way selector switch. It should be fairly simple, because I need to use a large number of them, and it should be able to source and sink a little but of current (at least 50mA).

    I know there are ICs called analog switches, but I can't find a good explaination of how they work. Do they act like a short when closed, or is there a significant resistance? Do they come in anything besides SPST?

    Thanks
    - Chris
     
  2. Bychon

    Member

    Mar 12, 2010
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    There are thousands of analog switch chips. You need to look at the data sheets for them until you find one that will carry 50 ma and have the voltage range that you need. The first one I looked at has 100 to 200 ohms of resistance and will carry 25 ma, but I'm not going to shop for the exact chip you need, only knowing that it should be a quad and pass 50 ma. Go to www.mouser.com and type in, "analog switch". You will find several thousand chips and their data sheets.
     
  3. Envergure

    Thread Starter Member

    Jan 14, 2010
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    0
    Thanks Bychon, but I'm still stumped. I understand how analog switch ICs work, but they only seem to be available in SPST and occasionally SPDT. What I need is, I think, nP4T (some number n of linked 4-way selector switches). I guess I could make them fron discrete transistors....

    I found some "multiplexer switch ICs," but I'm not sure what they do. The datasheets always contain a maze of logic gates that I can't make sense of.

    FYI I've never built any electronics in my life besides a Paia theremin kit. I have a breadboard, but no components to put in it yet.

    thanks
    - Chris
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    What are you wanting to do? And why would you need such a xP4T switch opposed to a few DPDT wired together? There are tips and tricks for all of this stuff.

    Analog computers used many, many switch types. So unless your inventing something way outta here, what you need is probably available.

    What are your input and output requirements? If you draw up what you want the switch to do, Im sure you can get a few recommendations
     
  5. Bychon

    Member

    Mar 12, 2010
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    I think the "wiring them together" is what has original poster stumped. The unknown input information (that is telling which switches should be closed) has to be sorted out with logic gates so it closes the right switches. Then the unknown supply voltage will pass through the switches to the unknown, 50 milliamp load.

    With so many things unknown, it is impossible to name which parts will do the job, and nobody wants to spend time designing something that probably won't work because they didn't know exactly what it was supposed to listen for or what it is supposed to apply some voltage to.
     
  6. BMorse

    Senior Member

    Sep 26, 2009
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    The op is looking for a way to have 1 input and distribute that to one of 4 outputs...
    like a 1 of 4 selector but as an analog switch.... something like this perhaps (MAX4618 4 to 1 Mux)?? >> http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2064

    B. Morse
     
  7. BillB3857

    Senior Member

    Feb 28, 2009
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    A 4066 is a quad switch.
     
  8. BMorse

    Senior Member

    Sep 26, 2009
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    But it is a quad bilateral analog switch, will not work for what the op wants, either just 1 input that can be routed to four outputs, or 4 inputs that can be individually routed to 1 output.... the 4066 has 4 inputs/outputs and 4 control lines to top it off....


    B. Morse
     
  9. BillB3857

    Senior Member

    Feb 28, 2009
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    So how is he going to select one of four paths without control lines?
     
  10. BMorse

    Senior Member

    Sep 26, 2009
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    well you still need control lines :rolleyes:, but some analog mux's only use 2 inputs to control up to 4 outputs, or 3 to control 8, etc... 4 controls for 4 I/O's seems a bit "low tech" IMO....


    B. Morse
     
  11. retched

    AAC Fanatic!

    Dec 5, 2009
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    BMorse uses a retinal scanner to unlock his front door.....and start his car.
     
  12. BillB3857

    Senior Member

    Feb 28, 2009
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    I use the KISS principle. Too lazy to look up the high tech new stuff.
     
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