# How to measure Rout & Rin using Cadence Analog Design?

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#### richloo

##### Full Member level 1

Hi, i am new to cadence software. Can anyone tell me the step to measure input resistance and output resistance of a circuit? Thanks in advance!

#### Fom

Using calculator. Divide VS/IS for DC analysis, VF/IF for AC analysis, VT/IT for transient analysis. Then plot it.

Points: 2

### Andreew

Points: 2

#### djalli

richloo said:
Hi, i am new to cadence software. Can anyone tell me the step to measure input resistance and output resistance of a circuit? Thanks in advance!

There is no point in discussing input/ouput resistance (better term would be impedance) in DC. So it is AC.

I am not so familiar with what Cadence you are reffering but if you are using OrCAD you can absolutely you can make input/output admitance/impedance vs. frequency.

What version?

mhjedaboard

### mhjedaboard

Points: 2

#### djalli

cadence + input + output impedance

In any of the case of what Cadence Product you have here is how you guys can do in cadence OrCAD.

See pictures. Simulation must be AC sweep.

#### dwang_w

##### Member level 1
how to measure the output impedance orcad

for example; i want to measure the output impedence of bias current source which is made of NMOS, what can i do?

#### richloo

##### Full Member level 1

As the case i wan to measure i/p and o/p impedance of an amplifier... how can i do that? i mean in Cadence IC50. Or else i have to goto result browser to find the rout for each transistor and write out all the nodal equation... any other fast method?

#### djalli

I do not know in Cadence IC50. I have never used this product. Sorry guys.

What I said for the above is for OrCAD.

I can tell you in also in A g i l e n t A DS and Ansoft Designer.

#### Ruritania

##### Member level 5

Hi,

(1). DC Rin and Rout: as what is said in the textbook, using a test voltage source to get the DC current, then R=V/I...

(2). Small signal Zin and Zout: just perform the S-Parameter simulation, no matter the simulator is Cadence or ADS.

Hope this helps.

Ruri

himansg

Points: 2

### himansg

Points: 2

#### eng_Semi

##### Full Member level 6
measure input resistance

Fom said:
Using calculator. Divide VS/IS for DC analysis, VF/IF for AC analysis, VT/IT for transient analysis. Then plot it.

Also from the calculator u can draw the real and imaginary parts, each in a separate curve

### richloo

Points: 2

#### xiongshoufen

##### Member level 3

the above explaination is good, thanks!

angbong

Points: 2