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aamar

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Germany

Behavioural modelling in HSpice
Feb 24^th, 2006, 2:46am

Hallo,
Is there a way to describe behavioural model to be used in HSpice (the model should include conditional statments)? (something like SpectreHDL with Spectre netlists).

i.e. I have a voltage controlled current source which depends on the Gate-Source voltage of a transistor, where the source is not constantly defined since it depends on the direction of the current in the transistor.

Best regards,

amar

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Geoffrey_Coram

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Re: Behavioural modelling in HSpice
Reply #1 - Feb 24^th, 2006, 6:13am

Some HSpice licenses include hsp-vacomp for Verilog-A compilation (not the "basic" hspice, but a somewhat more expensive one).

Also, HSpice allows fairly general expressions in their dependent source equations; you can include absolute values, and you may be able to include conditional expressions '(vds>0) * expr1 + (vds<=0) * expr2'

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aamar

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Re: Behavioural modelling in HSpice
Reply #2 - Mar 6^th, 2006, 6:38am

Dear Mr. Coram,

Thanks for your reply,

I don't have the -vacomp license.

and since you replied and I am searching in the Hspice manual for such conditional commands but I can't find it, can you tell me plz what exactly should I search for.

By the way, the only conditional possibility is included in N,PPWL sources, but it is not helpful in my case because the expression which I am using is depending on two values (i.e. bsource (voltage, current)) and in the G vccs PWL source I think I can only define the current depending on one parameter.

The other solution which I am trying is a two position ideal switch, which is controlled with �the source drain voltage and it should switch between two models (subcircuits).

Note: I have done it already with spectreHDL and spectre.

Thanks again

aamar

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Geoffrey_Coram

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Re: Behavioural modelling in HSpice
Reply #3 - Mar 15^th, 2006, 6:02am

Without knowing exactly what you are trying to do, I'm having a little trouble helping. I'm a little concerned that putting in conditional statements may introduce a discontinuity that you might not really want.

If you want something that depends on both V and I, you could certainly convert the I to a V using a CCVS, and then combine the two Vs with a two-input VCVS.

Also, consider using a voltage-controlled resistor. I found this equation

Rpure 3 4 'Rsh/mf*(l-dl)/(w-dw)*tfacp*(1+pvcp1*(tanh(pvcp2*abs(v(3,4)/(l-dl))+pvcp3)-tanh(
pvcp3)))'

in an HSpice model file.

HSpice certainly gives you enough rope to hang yourself.

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