The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> Circuit Simulators >> A question on the transient analysis of HSPICE
https://designers-guide.org/forum/YaBB.pl?num=1184217808

Message started by dandelion on Jul 11^th, 2007, 10:23pm

Title: A question on the transient analysis of HSPICE
Post by dandelion on Jul 11^th, 2007, 10:23pm

Hi,
I have a question on the HSPICE tramsient analysis. My circyuit is a triangular wave gennerator. I found the waveform is good before 1ms. But when after the 1ms, the waveform becomes not so smooth. I checked the simulator and i found the time step becomes loose after 1ms. Key point here is the block is always in steady state from the begining.

I tried the Smartspice, it is OK and no have this phenominon.

Anyone pls. tell me why?

Thank s a lot!

Title: Re: A question on the transient analysis of HSPICE
Post by ywguo on Jul 15^th, 2007, 8:04pm

Hi,

What is the period of your triangular wave generator?

What is the step size of your .tran command? Do you set .option method = gear instead of the default method=trag? What does the steady state mean?

Yawei

Title: Re: A question on the transient analysis of HSPICE
Post by dandelion on Jul 15^th, 2007, 11:45pm

ywguo wrote on Jul 15^th, 2007, 8:04pm:

Hi,
The time point step size become loose after 1ms. The simulator use the default algorithm. The steady state mean the circuit have veru quick startup time because it is RC oscillator. The frequncy is about 350KHz.

Pls. comment!
Thanks

Title: Re: A question on the transient analysis of HSPICE
Post by ywguo on Jul 20^th, 2007, 10:01am

Hi,

It is better to set the step size in .tran command less than one tenth of the triangular waveform generator. I guess that the step size is too large in your simulation.

Best regards,
Yawei