Page 61 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

LESSON 30 - 33 : Electronics Circuit Simulation

Objectives

At the end of this lesson you shall be able to
• state the literally components available in the circuit
• simulation software.

Electronic Circuit simulation is a process in which a model of an electronic circuit is created and analyzed using
various software algorithms, which predict and verify the behavior and performance of the circuit. Since fabrication
of electronic circuits, especially integrated circuits (ICs), is expensive and time-consuming, it is faster and more
cost-effective to verify the behavior and performance of the circuit using a circuit simulator before fabrication.
There are different types of circuit simulators catering to varied needs across the accuracy-performance/capacity
spectrum. At one end of the spectrum are analog simulators that solve accurate representations of electronic
circuits. They offer high accuracy and are commonly used to simulate small circuits. At the other end of the spectrum
are digital simulators that use functional representations of electronic circuits, typically described using hardware
description languages (HDL). These offer the highest performance and capacity, but at relatively lower levels of
accuracy. Digital simulators are commonly used to simulate very large circuits.
Types of Electronics Circuit Simulation
There are three basic types of circuit simulation: analog, digital, and mixed mode.
Analog circuit simulation involves the use of highly accurate models (i.e., representations) of the electronic circuit
to achieve high accuracy. The models include non-linear, linear, and simpler table-based representations of the
various electronic devices in the circuit. Analog simulation can run in different modes. These include AC (frequency
domain), DC (non-linear quiescent), and transient (time-domain). All analog simulators employ algorithms to
mathematically analyze the behavior of the electronic circuit in these different modes. They all share the quality
of solving matrices to predict the performance of the electronic circuit. Signals are propagated as continuously
varying values.

There are two primary types of analog circuit simulators
SPICE and Fast SPICE
SPICE simulators use highly accurate non-linear and linear models of electronic devices to analyze the behavior of
the circuit. SPICE simulators employ many different integration methods, such as Forward Euler, Backward Euler,
and Newton-Raphson as well as matrix decomposition techniques to compute the response of the entire circuit
(i.e., mathematical representation) at every single time point in the simulation period of interest.
By contrast, Fast SPICE simulators use simpler table-model representations of electronic devices to analyze circuit
behavior. They employ sophisticated algorithms to reduce the complexity of the circuit and partition the circuit based
on various criteria, essentially creating a simpler and more modular circuit representation. This representation is
then selectively evaluated at a given time point in the simulation period of interest, a process that greatly improves
the performance and capacity of the simulation. Fast SPICE simulators offer various simulation knobs to help
balance the tradeoffs between simulation accuracy and performance.

Digital circuit simulation involves the use of simpler models of electronic circuits. These models are typically created
using HDL. In digital simulation, rather than propagating continuously varying signals, a few discrete voltage levels
(primarily logic 0 and logic 1) are propagated. The methods to propagate these signals have varying degrees of
accuracy regarding the propagation delay of the logic levels through the circuit. This method of simulation allows
much larger circuits to be simulated in less time with fewer computer resources when compared to analog simulation.
Mixed-mode circuit simulation combines the analog and digital simulation approaches. The circuit is partitioned
between the two regimes to support the correct level of analysis detail for each part of the circuit. Analog simulators
(SPICE and Fast SPICE) are used for the analog analyses and a digital simulator is used for the digital analyses.
This method of simulation allows for much larger circuits to be simulated in less time with fewer computer resources
when compared to analog simulation.

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