Specifyng Diode Forward Voltage in PSpice Schematics

Thread Starter

akhuller

Joined Jul 28, 2016
5
Hi! I'm new to using PSpice Schematics, and I was wondering how one can specify the forward voltage of a diode.

The circuit is here below, with it continuing till the 10 th capacitor, C10. What diode model should I use, and how do I specify the forward voltage to be 1.4 V? I've uploaded my efforts for your reference as a .sch file.



Thank you so much!
 

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KL7AJ

Joined Nov 4, 2008
2,229
Here's some detailed information from the LTspice manual. Depending on how elegant your modeling needs to be, you can either choose a stock diode, or model the IV curve manually. I don't think you'll find a "normal" diode with a 1.4 V forward drop though, but you can synthesize that with a couple of diodes in series.

Eric
 

crutschow

Joined Mar 14, 2008
34,280
The diode model determines the forward voltage.
Just select a diode with the required reverse voltage and forward current rating.
What type of diode has a 1.4V forward drop?
Just putting two silicon junction diodes in series will give about a 1.4V drop.
 

Thread Starter

akhuller

Joined Jul 28, 2016
5
Thank you so much!! I'm putting two 1n4002 Diodes to get 1.4V forward voltage, since I read that they are Silicon diodes, and have 0.7 V FV approximately. I hope that's correct.
 

KL7AJ

Joined Nov 4, 2008
2,229
Thank you so much!! I'm putting two 1n4002 Diodes to get 1.4V forward voltage, since I read that they are Silicon diodes, and have 0.7 V FV approximately. I hope that's correct.
Yep.
And...if you want to experiment some, many LEDs have about a 1.4 Volt forward drop.
 

Thread Starter

akhuller

Joined Jul 28, 2016
5
Yep.
And...if you want to experiment some, many LEDs have about a 1.4 Volt forward drop.
Awesome!! Thank you so much! I have one last question for me to be done with this circuit. I need to measure the current vs time across the last capacitor (100uF) in the picture.
How do I do this?
When I press simulate, I get a graph. I changed the X-axis variable to I(current across that capacitor) and for the Y--axis, I put user-defined 0s to 10000Ms. Is this correct?
Thanks again.
 

SLK001

Joined Nov 29, 2011
1,549
I need to measure the current vs time across the last capacitor (100uF) in the picture.
How do I do this?
You use a transient analysis to do time dependent simulations.

Looks like you are trying to make a voltage multiplier for high voltages. A lot of high voltage diodes are two (or more) diodes in series, thus the 1.4V forward voltage. Your 1N4002 has a low breakdown voltage - you might want to use a 1N4007, which has a breakdown voltage of 1000V. You need to make sure your diodes can take the voltage. What ultimate voltage are you looking for?
 

Bordodynov

Joined May 20, 2015
3,177
i=is*(exp(Vd/(25.8mV *n))-1) ==> standard is=1e-14 ==>
n=(Vd/25.8mV)/ln(i/is) i=100mA=0.1 Vd=1.5 is=1e-14 ==> (1,5/25,8e-3)/ln(0,1/1e-14) = 1,942283013879 ==>
.model d1_5V d is=1e-14 n=1.942283013879

Draft317.png
 
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Thread Starter

akhuller

Joined Jul 28, 2016
5
You use a transient analysis to do time dependent simulations.

Looks like you are trying to make a voltage multiplier for high voltages. A lot of high voltage diodes are two (or more) diodes in series, thus the 1.4V forward voltage. Your 1N4002 has a low breakdown voltage - you might want to use a 1N4007, which has a breakdown voltage of 1000V. You need to make sure your diodes can take the voltage. What ultimate voltage are you looking for?
Thank you for your reply. The final voltage should be 1200V.
 
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