Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Measuring Input or Output Capacitance of a buffer

Status
Not open for further replies.
A

ashourism

Newbie level 6
Joined
May 17, 2012
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Egypt
Activity points
1,381
Hi

i am trying to measure the input and output capacitance of a buffer stage (for example) as i need to measure several other stages

i set up the following circuit

Capactiance Meas.png

and i set the input voltage to 1.2 with AC Magnitude and Amplitude to 1.2 , also vdd is set to 1.2

then i calculated Zin = I/1.2 * f

however i get extremely variable outputs as in files and also no imaginary parts get in the output csv file from Cadence how is possible?

also how am i supposed to measure the output capacitance

Thanks

- - - Updated - - -

So i made a mistake by dividing by 1.2 i divided by 1 and now i have a linear line with frequency but this is the total input Zin how i get the Input Capacitance (Imaginary)?
 

The change in impedance with frequency is the part caused by the capacitance. You can calculate the capacitance value from that.
 
so i used Cadence calculator to get the imaginary part of (I/V) then averaged it to get the slope this will be the capacitance?

What about the output i tried to the same technique but i got a non-linear curve
 

The output capacitance could vary slightly with signal due to the transistor junction capacitance change with bias voltage.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top