positive to negative voltage regulator?

Discussion in 'General Electronics Chat' started by jut, Jun 14, 2009.

  1. jut

    Thread Starter Senior Member

    Aug 25, 2007
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    Is there an IC that will take in a positive DC voltage and output a negative DC voltage?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. jut

    Thread Starter Senior Member

    Aug 25, 2007
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  4. SgtWookie

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    It's selectable x1 or x10 amplification.

    The pot on the output gives you the capability to adjust the amplification to some arbitrary level between 0 and x10.
     
  5. jut

    Thread Starter Senior Member

    Aug 25, 2007
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    Ah, I see it now, thanks.

    I'm trying to understand this circuit.

    The "AC Coupling, 1M Impedance" section of the circuit is a high pass filter, right?

    In the "150V input protection" part, what does the 47k resistor in parallel with the 100pF cap do?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    No, it's more of a bandpass filter. C1 blocks DC. R1 keeps the node floating around 0v. C2 acts as a short to ground for high frequency signals.

    It limits current through D1/D2 if the input voltage exceeds the voltage rails.
     
  7. jut

    Thread Starter Senior Member

    Aug 25, 2007
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    Are you sure? I calculated the frequency response by hand and then using "ac analysis" in multisim; both gave the same result, a high pass filter.


    Ok, makes sense.

    I don't know what you mean by this.

    Ok, makes sense.

    I can see how the resistor limits current, but why put it in parallel with a cap?

    Thanks for the help BTW. :)
     
  8. SgtWookie

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    It'll look like that if you're only sweeping lower frequencies. If you go high enough in frequencies, C2 will start attenuating them.

    re: keeps the node floating around 0v
    OK. Run a transient analysis on it feeding the input a 1kHz square wave from 0v to 5v, for about 30mS. You'll see that the 1 MEG resistor pulls the signal down to average around 0v. Without that resistor, the average voltage level would float randomly.

    Try doing an AC analysis on it.
     
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