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Simulators >> Circuit Simulators >> Problem with diode in Hspice
https://designers-guide.org/forum/YaBB.pl?num=1353856180

Message started by shiju on Nov 25^th, 2012, 7:09am

Title: Problem with diode in Hspice
Post by shiju on Nov 25^th, 2012, 7:09am

I am trying to simulate a diode using a square wave. code is given below

*diode test
v1 1 0 pulse(0 5 1n 1n 1n 4m 10m)
D1 1 2 D1
.model D1 D()
R1 2 0 1k
.tran 1m 5m
.plot tran v(3)
.end

But when the diode at forward bias, output voltage changes many times. Then I simulate diode with sinusoidal signal, it works properly. Why did this happened and how can I eliminate this?

Title: Re: Problem with diode in Hspice
Post by raja.cedt on Nov 25^th, 2012, 10:48am

hello,
whats your question? try to draw fig and ask. looks like .plot tran v(3) wrong, becaz there is no node with 3, i guess it is 2.

Thanks,
Raj.

Title: Re: Problem with diode in Hspice
Post by shiju on Nov 25^th, 2012, 11:51pm

I correct to .plot v(2). But still the problem exist. I explain what is my problem. First I simulate diode with sine wave. Code and result is given below
*diode test
V1 1 0 sin(0 10 500)
D1 1 2 D1
.model D1 D()
R1 2 0 1k
.tran 1m 5m
.plot tran v(2)
.end

Then I simulate same circuit with square wave. code are given below. Result given in my first post.
*diode test
v1 1 0 pulse(0 5 1n 1n 1n 4m 10m)
D1 1 2 D1
.model D1 D()
R1 2 0 1k
.tran 1m 5m
.plot tran v(2)
.end
That at tme 1 to 4ms output voltage changes many times. Thats my problem. what is its reason

Title: Re: Problem with diode in Hspice
Post by raja.cedt on Nov 26^th, 2012, 12:14am

hello,
looks like some problem with simulator, try to change some parameter like rise,fall time little bit it may work. There is no problem with your code i ran the same and i got the following result. I guess it's not a problem with diode,otherwise it wouldn't gave correct result with sinusoidal. To make your self happy you could plot diode VI characteristics .

Have fun,
Raj.

Title: Re: Problem with diode in Hspice
Post by shiju on Nov 26^th, 2012, 8:17am

My code is work properly in orcad pspice. But it is not working in HSPICE

Title: Re: Problem with diode in Hspice
Post by Geoffrey_Coram on Nov 26^th, 2012, 12:44pm

I noticed your AvanWaves version is 4 years old (2008). Are you using a recent version of HSpice?

You might want to add some capacitance to your circuit; some simulators have trouble picking timepoints if there is no dynamic behavior.

Title: Re: Problem with diode in Hspice
Post by shiju on Nov 27^th, 2012, 8:11am

Yes I am using avanswave 2008. can I get Latest version of Hspice from any website? Can you help me to add capacitance to this circuit. I dont understand fully about what you said.

Title: Re: Problem with diode in Hspice
Post by Geoffrey_Coram on Nov 27^th, 2012, 12:09pm

I don't think you can get HSpice from a web site; most places (companies, universities) that have HSpice have a support contract with Synopsys that specifies how/when they get updates.

Regarding capacitance, set the CJ parameter:

.model D1 D( CJ=1e-12 )

Title: Re: Problem with diode in Hspice
Post by shiju on Nov 27^th, 2012, 8:59pm

Thank you. It is working.