Simulation of ft and gm/Id in Cadence

1.Simulation of ft

The transistor ft is simulated with current gain in ac simulation.  Below is a simple schematic to simulate ft.

Plot the current gain:

dB20(i("NM0:d" ?result "ac-ac")/i("NM0:g" ?result "ac-ac"))

Or you can use the results browser under "Tool" menu to show the results:

1. Open the Results Browser
2. Select the output data directory, raw/psf/...
3. Select the results, ac-ac
4. Right mouse button on NM0:d and select calculator
5. Right mouse button on NM0:g and select calculator
6. Select divide, "/" from the calculator keypad
7. Select, dB20 from the "Math" functions

Refer to http://www.cadence.com/Community/blogs/rf/archive/2008/08/09/simulating-mos-transistor-ft.aspx

Netlist:

simulator lang=spectre

global 0

parameters ICE=100u VCE=5

//

// these model files should be available in the samples directory

//

include "./models/NPNlower.scs"

include "./models/cornerMos.scs" section=TNTP



V0 (net014 0) vsource dc=VCE type=dc



// MOSFET ft

// NOTE: the element instance names have been changed

// the default names are shown in the bjt section

// IREFERENCE --> 0V voltage source

// IFEEDBACK --> current-controlled, current source

IIN (net014 net9) isource dc=ICE mag=1 type=dc

IREFERENCE (net6 0) vsource dc=0 type=dc

IFEEDBACK (net9 0) cccs gain=1.0 probe=IREFERENCE

NM0 (net014 net9 net6 0) nmos24 w=24u l=1.5u m=10



// BJT ft

IIN_BIPOLAR (net014 net025) isource dc=ICE mag=1 type=dc

IREF_BIPOLAR (net012 0) vsource dc=0 type=dc

IFDBK_BIPOLAR (net025 0) cccs gain=1.0 probe=IREF_BIPOLAR

Q0 (net014 net025 net012 0) NPNlower



ac ac start=1 stop=100G annotate=status

save NM0:g NM0:d Q0:c Q0:b 

2.Simulation of gm/Id

the simpliest way of simulate it is:

Run DC analysis. Sweeping variable is Vgs (just connect Vgs to Vdc and sweep Vdc voltage).


Then using calculator take IS of drain or drain current. Click "Special function" and select "deriv"

Then click "x<->y", then "/"(devide) and "erplot"

or you can refer to:

http://www.eecs.tufts.edu/~ryun01/gmid_ruida.pdf