1. An Introduction to Verilog-A: Transitioning from Verilog
Tutorial 1
An Introduction to Verilog-A: Transitioning from Verilog

2. Lesson Plan (Tentative)
Week 1: Transitioning from VHDL to Verilog, Introduction to Cryptography
Week 2: A5 Cipher Implementaion, Transitioning from Verilog to Verilog-A
Week 3: Verilog-A Mixer Analysis

3. Analog Verilog (Verilog-AMS)
Verilog introduced as IEEE Standard 1364
Dire need for analog circuits to be modelled as a language
VHDL and Verilog come up with analog equivalents: AHDL and Verilog-AMS (Analog and Mixed Signal)

4. New Types in Verilog-A Integer/Real (same as Verilog)
Electrical (electrical wire)
Parameter (parameter constants)
Genvar (local variables eg for loops and such)

5. Parameters
Example:
Parameter real gain = 1 from [1:1000];
Second keyword real specifies optional type (real or integer)
From is used to specifies optional range of the parameter. [] is used to indicate that the end values are allowable while () means end values are not.

6. Parameters
Parameters cannot be changed at run time, but can be changed at compile time using defparam
Example:
module annotate;
defparam
tgate.m1.gate_width = 5e-6,
tgate.m2.gate_width = 10e-6;
endmodule

7. Parameters Can also exclude ranges, eg Can be arrayed, eg
Parameter real res = 1.0 from [0:inf) exclude (10:20) exclude 100;
Can be arrayed, eg
Parameter real poles[0:3] = {1.0, 2.0, 3.83, 4.0};
Can be strings, eg
Parameter string type = “NPN” from { “NPN”, “PNP” };

8. Operators
Mostly same as Verilog, but has extra functions for analog design
Built-in mathematical functions:
ln(x), log(x), exp(x), sqrt(x), min(x,y), max(x,y), abs(x), pow(x,y), floor(x), ceil(x)
sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), sinh(x), cosh(x), tanh(x), asinh(x), acosh(x), atanh(x)

9. Operators (con’t) Voltage/Current access:
V(b1), V(n1) access the branch voltage and node voltage wrt ground
V(n1,n2) accesses the difference between n1 and n2
I(b1), I(n1) access the branch current and node current flowing to ground

10. Operators (con’t) Voltage/Current access:
I(n1,n2) accesses the current flowing between n1 and n2
I(<p1>) accesses the current flowing into p1, a port

11. Analog Operators (Filters)
Cannot be placed in any loop or conditional (for, while, if, case, repeat) because internal state must be maintained
Only in an analog block
Argument list cannot be null

12. Analog Operators ddt(x), calculates the time derivative of x
idt(x,opt_ic), calculates the time integral of x (with or without initial condition)
laplace_zp, laplace_zd, laplace_np, laplace_nd (various laplace transforms)

13. Analog Operators Analysis types Noise models
Analysis() returns true(1) if analysis done is of that type (AC, DC, tran, noise, etc)
Noise models
Can use white_noise, flicker_noise, noise_table

14. User-Defined Functions
Syntax:
analog function real geomcalc;
input l, w ;
output area, perim ;
real l, w, area, perim ;
begin
area = l * w ;
perim = 2 * ( l + w );
end
endfunction
Called as follows:
dummy = geomcalc(l-dl, w-dw, ar, per) ;

15. Signals and Models
Let’s take an example of a resistor (modelled as a voltage-controlled current source)
module my_resistor(p,n);
parameter real R=1;
electrical p,n;
branch (p,n) res;
analog begin
V(res) <+ R * I(res);
end
endmodule

16. Signals and Models (con’t)
Other current/voltage sources:
V(out) <+ A * V(in); //VCVS
I(out) <+ A * V(in); //VCCS
V(out) <+ A * I(in); //CCVS
I(out) <+ A * I(in); //CCCS

17. Signals and Models RLC Circuit model Series: Parallel:
V(p, n) <+ R*I(p, n) + L*ddt(I(p, n)) + idt(I(p, n))/C;
Parallel:
I(p, n) <+ V(p, n)/R + C*ddt(V(p, n)) + idt(V(p, n))/L;

18. Simple Amplifier Example: module amp(out, in); input in; output out;
electrical out, in;
parameter real Gain = 1;
analog
V(out) <+ Gain*V(in);
endmodule

19. Mixed Signal Models Note that wires are used with electricals.
Example: one-bit DAC
module onebit_dac (in, out);
input in;
inout out;
wire in;
electrical out;
real x;
analog begin
if (in == 0)
x = 0.0;
else
x = 3.0;
V(out) <+ x;
end
endmodule
Note that wires are used with electricals.
The digital signals in this context are represented as bits

20. Conclusions
Verilog is so useful that it has been redesigned for analog/mixed signal applications
Designer Guide (surprisingly easy to read)