half wave rectifier + voltage increase

Discussion in 'Electronics Homework Help' started by Mobin, May 4, 2017.

1. Mobin

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0
May 1, 2017
hi!
I've been assigned to design the simplest circuit to get the Output voltage(green) from the input(red) and simulate it by OrCAD:

I have done this:

And the output was:

NOW the problem is that the output starts at about 0.06s and end at 0.44s while it must be between 0.00s and 0.50s
Is it a problem of diode model?
we've just been taught about BJT Transistors and I'm not sure if using them is necessary or not?

Last edited: May 4, 2017
2. Harald KappModeratorModerator

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Nov 17, 2011
When the input voltage is 0 or negative, the diode is not conducting and the output voltage is determined by V3. Therefore V3 = 3 V is correct.

Your idea of using V2 to offset the input voltage is also correct. The voltage you have chosen is not correct.
Consider the time t=0 where the AC input voltage is 0 V. What is the voltage you need to apply to V2 to make the diode pass 2 V to R1? It is not 1.6 V.

Next consider the point where the AC input has its top amplitude (V(V1) = 2 V). What is the output voltage in that case? Hint: it is too high.
What could you do to reduce the output voltage without afflicting the voltage for V(V1) <= 0V? Hint: Insert another component in the output circuit. Which one and where Is up to you.

Harald

btw.: as this is an assignment, I'll move the thread to the appropriate section of our forum.

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3. Mobin

13
0
May 1, 2017
thank you
I think i can use a transformer but I'm not sure if it's correct and also how to put one in orcad

4. Harald KappModeratorModerator

11,794
2,749
Nov 17, 2011
You don't need a transformer, plus a transformer would not let pass the dc offset.
Look at the output volateg with only R1 (and not the unknown additional component) in place. What is the value? What can you do to reduce teh value without a transformer. Hint: You already have R1 in place.

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