Pspice help...........

[engr_najam]

how can i develop a frequency dependent resistor in PSpice.
the expression of the resistor is given by

Resistance=100 * sqrt(freq)

will be waiting for ur kind reply....

 

[Rob B]

Just a guess as I have never tried it but can you add it as a parameter?

You may have to add the "Parameter" component from the "Special" library if I remember right.

 

[engr_najam]

but how can we then enter the frequency variable....

 

[FvM]

You can't use freq, but you can use functions of s in analog behaviour modelling, see the Pspice reference for details. However, in transient analysis, fourier transformation is implied when using s-variable, also with some filter models that are based on s-functions. This restricts the usable time dynamic and may reduce analysis accuracy considerably to my experience, sometimes producing very odd results.

 

[engr_najam]

plz reply in a bit detail along with screen shot. i m really in trouble

 

[dmk]

Make the circuit - cir.1.
Change the value of resistor - cir.2.
Call PARAM, open Properties, make a new column, name it "f" and give it a value (1kHz in the case) - cir.3. Dont forget to display the value (at least).
Put a voltage marker to watch the output - cir.4.
Make a new simulation profile and fill in: Time domain (transient), Run to time (5ms in case) and Maximum step size (50u in case) - cir.5.
Mark the option: Parametric Sweep, check as sweep variable "Global parameter", give the appropriate sweep type (Linear in the case) and define the name, start and end value, as well as increment (f, from 10Hz, to 10k, with step of 1kHz in this case) - cir.6.
Start simulation and watch the result - cir.7.

 

[ssajidhb]

slides for pspice

 

[engr_najam]

thats was indeed a very good try by [/b] dmk [/b], but how can i take the AC sweep of the circuit then.
simply i wanna plot it in such a way that it that i can see an impedance(resistance) changing with frequency in BODE plot.

 

[dmk]

Could you explain me a little bit more details? Because your question was only for frequency dependent resistor?