*LAB2 Static Load Inverters
 
*
* Power supplies
*
 
v_vcc vcc 0 vccr
v_vss vss 0 vssr
 
.global vcc vss
 
*
* Circuit Stimulus
* V_in is a voltage source connected between the nodes 'in' and 'vss'
V_in in vss dc 0
*
* Corner information
*
.include '/ecad/local/cadence/cysrc/t/2.0/hp14tb/models/trtc.cor'
.include '/ecad/local/cadence/cysrc/t/2.0/hp14tb/models/tt.cor'
.temp 27
.param vssr=0 vccr=3.3 vbbr=0
 
*
* Options information
*
.options nomod post scale=1e-6
 
*
* Extra devices
*
* Defines another power supply needed for the subcircuit X2
V_vcc2 vcc2 vss vccr
*

*Defines a dependent voltage source Ein2
Ein2 in2 vss vol='v(in)+0.1'
*The above line defines the dependent voltage source
*the value of Ein2 is the value of v(in) + 0.1v
*Note that for using Ein2 in this way, we should have
*first defined the primary source v(in).


*Another dependent voltage source to
*measure the slope
Eslope slope vss vol='(v(out2) - v(out))/0.1'

*Defining a subcircuit
*replace subckt_name with any name of your choice 
*replace spiceckt_name with the name of spice circuit file
.subckt subckt_name vcc vss in out
.inc 'spice_cktname.sp'
.ends subckt_name



*Instantiating a subcircuit
*Element name for subckt instantiation must begin with an 'X'
X2 vcc2 vss in2 out2 subckt_name


*To measure the resistance across the load element
*i(v_vcc) gives the current that is coming
*out of the supply v_vcc
*This current is the drain-source current in the load device
Eres res vss vol='(vccr-v(out))/i(v_vcc)'

*
* Analysis information
*

*This performs a dc sweep from 0 to vccr in
*steps of 0.01
.dc V_in 0 vccr 0.01

*put .measure statement for finding switching point here


.MEASURE dc lowest_output FIND v(out) when v(in) = vccr
* for the inverter the output is at its lowest when input is maximum 
*of vccr


*put .measure statement for highest_output here
*note that the output will be highest when the input is lowest ie vssr

.MEASURE dc voh FIND v(out) WHEN v(slope) = -1.0
*similarly write out the .measure statement for vil

.MEASURE dc vih FIND v(in) WHEN v(slope) =-1.0 cross=2
*similarly write out the .measure statement for vol
*note that on your tranfer char. there are 2 points
*at which the slope is -1. cross = 2 indicates the 
*second point at which the slope is -1.

*The gain of the inverter is dVoutput/dVinput = slope
*The slope is negative
*So the gain is max. when slope is min.
.MEASURE dc max_gain MIN v(slope)

*To compute the noise margin
*once you have voh and vih
.MEASURE dc nm_h param='(voh - vih)'

*Similarly obtain the nm_l parameter from vol and vil


*to include your ckt file add the ckt file name to the next line
.include 'spiceckt_name.sp' 


.end