[SI-LIST] Re: How to get the load capacitance of input buffer by means of HSPICE model
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: zhang_kun@xxxxxxxxxx
- Date: Wed, 23 Feb 2005 21:16:57 -0500
Zhangkun
A reasonably accurate and simple way to create a circuit of the
equivalent capacitance of the input buffer can be performed using HSPICE
and it's optimization capability. The proceedure is this.
Set up two parallel circuits.
Circuit 1:
Trapezoidal voltage source, 50 ohm series resistor, and the input buffer.
Circuit 2:
Trapezoidal voltage source, 50 ohm series resistor, and a capacitor to
ground
Parameterize the capacitor value.
Set up an HSPICE optimization and use a comparison between the voltage
at the input of the buffer and the voltage at the input of the capacitor
as your optimization comparison, and let the simulator run until
convergence.
Another method is tie two 50 ohm transmission lines to the input of the
buffer. Using an AC sweep, extract the transfer impedance across the
capacitor. With the input in place there will be an impedance to
ground. Z=1/((2*pi*f*C). From the slope you can calculate the capacitance.
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
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Zhangkun wrote:
>Dear all
>Now I have the HSPICE model of one input buffer. In order to simplify the
>simulation, I want to use a load capacitance to replace the buffer. How to get
>the load capacitance of input buffer? Please give me some advice.
>
>Best Regards
>
>Zhangkun
>2005.2.24
>
>
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