AIM-SPICE

SPICE is the most commonly used analog circuit simulator today and is enormously important for the electronics industry. SPICE is a general purpose analog simulator which contains models for most circuit elements and can handle complex nonlinear circuits. Aim–SPICE is a type of SPICE only and in Aim -SPICE CAD tool, circuit is designed by writing netlist. Netlist is defined as a circuit description in text form.

In Aim-SPICE, the operator has complete control during a simulation. Before a simulation starts, the circuit variables to be monitored during the run are selected and Aim-SPICE will graphically display  the progress of these variables during the simulation.

1.1.1    Netlist Format

The first line of the net list is the title line. This should contain pertinent information to the circuit and your file name. The next lines are for circuit parameters – as many as needed. The next section is for output control statements. The file is closed with an <.END> statement. Below is the syntax for various elements. Each parameter name starts with a specific letter followed by a user-defined name (i.e. R1, Cnew, Vout). The [ ] and the < > are not actually typed, they are for visual purposes only. Parameter components must be separated by spaces or tabs.

1.1.2    Parameter Syntax

Resistor:

R<name> [+ node] [- node] [value]

Capacitor:

C<name> [+ node] [- node] [value] [IC = <initial value>, optional]

Inductor

L<name> [+ node] [- node] [value] [IC = <initial value>, optional]

Independent Sources

I<name> [- node] [+ node] [value] [type] [transient spec]

V<name> [+ node] [- node] [value] [type] [transient spec]

Dependant Sources

VCVS: E<name> [+ node] [- node] [+controlling node] [-controlling node] [gain]

CCCS: F<name> [+ node] [- node] [Vbranch] [gain]

VCCS: G<name> [+ node] [- node] [+controlling node] [-controlling node] [gain]

CCVS: H<name> [+ node] [- node] [Vbranch] [gain]

MOSFET

.MODEL [model name] NMOS <model parameters>

.MODEL [model name] PMOS <model parameters>

1.2      Output Analysis in Aim-SPICE

The simulator can calculate dc operating points, perform transient analyses, locate poles and zeros for different kinds of transfer functions, find the small signal frequency response, small signal transfer functions, small signal sensitivities, and perform Fourier, noise, and distortion analyses. SPICE allows performing many different operations in different types of SPICE and in different versions.

1.2.1    AC Analysis

AC small signal analysis is initiated by the .AC statement. AC analysis is used to calculate the frequency response of a circuit over a range of frequencies. The aim in AC analysis is to determine the AC voltage at every node in the circuit which is linear because of the small-signal approximation.

1.2.2    DC Analysis

DC Operating Point Analysis is initiated by the .DC statement. The analysis of nonlinear resistive circuits or equivalently the analysis of circuits at DC is an important first step in AC and transient analysis. In both cases nonlinear resistive analysis determines the initial starting point for further analysis incorporating energy storage elements such as capacitors and inductors.

1.2.3    DC Temperature Sweep Analysis

DC Temperature Sweep Analysis is initiated by the .TE statement. In a DC Temperature Sweep Analysis the operating temperature is swept over a user defined interval. The DC operating point of the circuit is calculated for every temperature value. The analysis has three parameters: Start temperature, stop temperature and increment. All parameters have unit ºC.

1.2.4    DC Transfer Curve Analysis

DC Transfer Curve Analysis is initiated by the .TF statement. In a DC Transfer Curve analysis, one or two source(s) (voltage or current sources) are swept over a user defined interval. The dc operating point of the circuit is calculated for every value of the source(s). Source Name is the name of an independent voltage or current source, Start Value, End Value and Increment Value are the starting, final and increment values respectively.

1.2.5    Noise Analysis

Noise Analysis is initiated by the .N statement. Noise Analysis computes device-generated noise in a circuit.

1.2.6    DC Operating Point Analysis

This analysis calculates the DC operating point of a circuit. It has no parameters.

1.2.7    Pole-Zero Analysis

Pole-Zero Analysis is initiated by the .PZ statement The Pole-Zero Analysis computes poles and/or zeros in the small signal ac transfer function. You may instruct AIM-SPICE locate only poles or only zeros. This feature may allow one of the sets to be determined if there is a convergence problem with finding both.

1.3      Importance of MOSFET Levels

In modern VLSI design, importance of accurate MOSFET design has arisen due to which AIM-SPICE supports 26 MOSFET models. The parameter LEVEL selects which model to use. The default LEVEL is LEVEL=1.

Before the selection of appropriate MOSFET model type to use in analysis, there is a need to know the electrical parameters that are critical to the application. LEVEL 1 model is most often used to simulate large digital circuits in situations where detailed analog models are not needed. LEVEL 1 models offer low simulation time and a relatively high level of accuracy for timing calculations. If there is a need of more precision (such as for analog data acquisition circuitry), then use of the more detailed models, such as the LEVEL 6 IDS model or one of the BSIM models can be done. For precision modelling of integrated circuits, the BSIM models consider the variation of model parameters as a function of sensitivity of the geometric parameters. The BSIM models also reference a MOS charge conservation model for precision modelling of MOS capacitor effects.

1.3.1    Available MOSFET levels in Aim-SPICE

AIM-Spice supports 26 MOSFET models. The parameter LEVEL selects which model to use. The default is LEVEL=1.

Different levels are as follows:

 MOSFET Levels in Aim-SPICE

Sr. No.	Models	Levels
1	Berkeley SPICE Models	1,2,3,6
2	Berkeley SPICE BSIM1 Model	4
3	Berkeley SPICE BSIM2 Model	5
4	MOSFET Model MOSA1	7
5	MOSFET Model NPMOSA1	8
6	MOSFET Model NPMOSA2	9
7	MOSFET Model NPMOSA3	10
8	Amorphous-Si TFT Model ASIA1	11
9	Poly-Si TFT Model PSIA1	12
10	Berkeley SPICE BSIM3v2 Model	13
11	Berkeley SPICE BSIM3v3.1 Model	14
12	Amorphous-Si TFT Model ASIA2	15
13	Poly-Si TFT Model PSIA2	16
14	Berkeley SPICE BSIM3 v3.2.4 and v3.3.0 Models	17, 18
15	Berkeley SPICE BSIM3SOI Model	19
16	Berkeley SPICE BSIM4 Models	20, 21, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32
17	EKV MOS version v2.6 Model	23
18	Berkeley SPICE BSIMSOI Model Version 4.0	35