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DPDT Question

  1. Nov 7, 2007 #1
    Are there any DPDT switch that can take negative input?
    i want to put a sinusoidal as input and use the output to go through a difference amplifier to create a rectifier.

    does it work the same if i put a DC offset so i only get positive sinusoidal input to DPDT, and then use the output to go through a difference amplifier? (maybe i need to subtract DC offset to get the equivalent as without no offset?)
     
  2. jcsd
  3. Nov 7, 2007 #2

    mgb_phys

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    A mechanical DPDT will obviously pass anything upto the breakdown voltage.
    Otherwise most CMOS mux chips will switch pretty close to the rail voltage, although a lot of high speed ones are made for switching video so only handle 0-1V levels.
     
  4. Nov 7, 2007 #3
    getting 2 of these max4564 ior dg469 should work i suppose. its a dual supply spdt
    thoughts?
     
  5. Nov 7, 2007 #4

    mgb_phys

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    The DG one claims to switch +/- 15V with the dual rail supplies.
    I used a similair single rail DG unit for a double correlated sampling setup once.
     
  6. Nov 7, 2007 #5
    actually this chip is probably not available, but doing a product search in vishay spdt dual supply yielded quite a number of chips. my signal is +-5v, i'll just supply it with +-12v

    another quick question
    when selecting, should i care about on resistance for the gate? what is the difference or function between say an on gate of 10ohm and one with 200ohm. lower resistance means less current supply i guess. so lower means better?
     
  7. Nov 8, 2007 #6

    mgb_phys

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    Lower on resistance means less power dissapated in the chip if you are sending a large current, it also means less voltage drop if the source of your signal isn't a stiff supply.
    At high speeds it also means a lower time constant for the circuit.
     
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