Signal cross switcher

Discussion in 'General Electronics Chat' started by chaos51, Jun 27, 2012.

  1. chaos51

    Thread Starter Active Member

    Jun 18, 2011

    This may ultimately be a very studpid question, and I probably should know the answer allready, but then again, being a noob with electronics, gives me the right to ask dumb questions (I hope ;o)

    I have two signals, A and B. They are analogue voltage readings (it is unimportant for the question where the signals come from, but they come from light sensors in this case).

    I have a chip that takes two analogue signals, and does processing on them. (a bit like a comparator, but the chip is something else)

    In any case neither the chip or the sensors are very interesting to me.
    As I intend to apply the principle to different chips, using different sensors.

    So, what I want to do is the following.

    Signal A, goes to input 1, Signal B goes to input 2, when a digital signal S is false. If S is true Signal A goes to input 2, and Signal B goes to input 1.

    A very easy way to do this it seems is by using a relay.

    Alternativly, I can concoct some schemes that do this with 4 FETs. It's a little like a H-Bridge but not really.

    My question is, are there ready made components that do this, and what is their name?

    I have thought about Multiplexer, but I am not quite sure it is the same.. Perhaps two multiplexer parallel may do it.

    I can imagine a H-Bridge being able to do it, but most motor driver H-Bridges switch between a high voltage and a ground. Swapping the ground and the high voltage on the chip will probably result in the chip not doing anything, as the ground is also ground for the logic in the chip.

    So.... Are there any ideas out there, what component type I am trying to find?

  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
  3. crutschow


    Mar 14, 2008
    Depending upon the voltage level of the signal you should be able to use a dual 4-channel multiplexer such as the CD4052.
  4. absf

    AAC Fanatic!

    Dec 29, 2010
    I guess this is what you wanted.:)

    The CMOS gates like 4016, 4066, 4051-4053 uses what they called bi-lateral (spelling??) switches. The switch was made using two mosfet connected back to back so you can pass analog signals through them. You may also use them in reverse, ie output becomes input and vice versa (correct me if I were wrong). You cannot do the same to the TTL multiplexers like 74151 or 74153.

    Last edited: Jun 27, 2012
  5. ArmbrusterJo

    New Member

    Jun 27, 2012
    The switch was made using two mosfet connected back to back so you can pass analog signals through them. [​IMG]
  6. chaos51

    Thread Starter Active Member

    Jun 18, 2011

    Now I have some avenues to investigate. ;o)
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Trying to make 4066 look like a DP-DT SW or Relay. Input V should be less than Vdd.
  8. praondevou

    AAC Fanatic!

    Jul 9, 2011

    Depending on your analogue signal processing chip/circuit certain parameters of multiplexers or CMOS switches DO matter.

    Charge injection, ON-resistance and leakage current, missing break-before-make action etc. can have an important impact on your measurement results.

    Also, some parameters of switches like the 4066 vary greatly with temperature.

    What switch is best suited depends on your application, clock switching frequency and adjacent circuitry.