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Homework Help: PSPICE simulation with Schematic of Waveform Selector

  1. Jan 29, 2013 #1
    1. The problem statement, all variables and given/known data
    Hi in response to my previous thread (principles behind the waveform selector circuit), I would now like to run a SPICE simulation using the PSPICE schematics software to obtain the theoretical values before entering my lab session. I have uploaded the schematic for your reference.

    2. Relevant equations
    Right now I have constructed the circuit in the program but I am unsure of which switch, transistor (BC548) and input signal to put in.

    Also if I want a square wave input, which settings do I need to configure?

    Assuming then the circuit is constructed perfectly, how am I going to observe the output at the switch?

    3. The attempt at a solution
    Kindly see attached for the circuit which I have constructed in PSPICE. I have left out the switch and the transistor. For the input signal I used a VSRC 5V power supply.

    Attached Files:

  2. jcsd
  3. Jan 29, 2013 #2

    rude man

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    Homework Helper
    Gold Member

    You're inputing just dc supplies? How do you expect to get any waveforms? And why did you omit the transistor???
  4. Jan 30, 2013 #3
    Well okay I did some research yesterday and found out that if I need a square wave generator I need to use VPULSE. Okay so I used that and instead of constructing the whole circuit, I constructed the circuit based on which switch I press on.

    I omitted the transistor because I didn't know which transistor to use.

    Please tell me if what I am doing now is correct.
    (please see attached for circuit setup and output waveform)

    Also can anyone tell me why when I input a 2V square wave pulse, the voltage that appears across the 4.7k Ω resistor is still 2V when it should have been 1.649V.


    Attached Files:

    Last edited: Jan 30, 2013
  5. Jan 30, 2013 #4


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    Staff: Mentor

    Instead of the switch, just record the waveforms at the nodes in the circuit that the switch would connect to. If you don't have the SPICE data for the BC548 than use any other small signal NPN transistor with a similar beta.

    You seem to have a time scale on your recording of seconds. It should be related to the period of the squarewave, to show just 2 or 3 complete cycles.

    R8 and R2 form nothing more than a potential divider. You renamed R8 to be R1? And you have accidently shorted it out! No wire connects to their junction.

    It would have been better to have this as a continuation of your earlier thread.

    Sadly, I can't help with SPICE details, I've forgotten too much.
    Last edited: Jan 30, 2013
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