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I want to add a cyclostaionary noise current ( 4*k*T*Gm(t) ) to a non-linear ( hard-limiter ) Gm block
Gm(t) = derivative( I(out)/V(in)).
But the moment I am doing Gm_t = ddx(I(out),V(in)); It is giving error.
Actullay, I ideally want to add white_noise(4*k*T*Gm_t) to I(out) finally.
It looks recursive. But could anybody please tell how this can be done.
The code is as given below.
// VerilogA for VERILOG_A_MODEL, HARD_LIMIT_GM, veriloga`include "constants.vams"`include "disciplines.vams"module HARD_LIMIT_GM(in,out); inout in,out; parameter real vtrans = 0; parameter real tdelay = 0 from [0:inf); parameter real trise = 1p from (0:inf); parameter real tfall = 1p from (0:inf); parameter real Gm=-5m;
electrical in,out; real vout_val;
analog begin @ (cross(V(in) - vtrans)) ; vout_val = V(in)>vtrans; I(out) <+ Gm * transition( vout_val, tdelay, trise, tfall);
Gm_t = ddx(I(out),V(in)); // HERE IT IS SHOWING ERROR
// Actullay, here, I ideally want to add white_noise(4*k*T*Gm_t) to I(out) .
I thought to create another block which senses the current "I1" input and voltage 'Vin" input and find the derivaive (dI1/dVin).
To test the individual block I gave a sine current source of 1.02GHz, amp=10mA to input I1 and a sine volatge source of to input 'Vin" of 1GHz and amp=1V.
But in the code it always evaluates (dI1/dVin) ( Gm_t in the code ) to ZERO.
Can anybody tell what is the issue ?
My code is as below:-
/ VerilogA for VERILOG_A_MODEL, GM_T_NOISE, veriloga`include "constants.vams"`include "disciplines.vams"module GM_T_NOISE(in_v,in_i,out,vx); inout in_v,in_i,out,vx;
analog begin Gm_t=ddx(I(in_i),V(in_v));
I(out) <+ Gm_t;
$strobe("GM = %rs \n", Gm_t);
V(in_i,vx) <+ 0; // To make short between in_i & vx
// During simulation node ' vx ' is connected to ground