Sensitivity Analysis in Electrical Circuits:

What is Sensitivity Analysis in Electrical Circuits?

Sensitivity analysis identifies which components have parameters critical to the measurement goals of the circuit design.

Usually the sensitivity is done by the simulation tools like Pspice. These tools perform advanced analysis like sensitivity analysis apart from the functional simulation.

[It is good to know what is Simulation and Simulation tool before proceeding further about advanced analysis using the simulation tools]

Definition of Simulation:

The imitation of the performance of a process, device or system is called as simulation. It can also be defined as the use of a mathematical model to represent a physical process, device, or system.

  • Computer simulation provides us with a powerful and cost-effective tool for designing, simulating and analysing a wide variety of electronic circuits.
  • Now a days the computer software packages designed for this task have become more sophisticated and easy to use.
  • Several of the most powerful and popular packages are available at low-cost or with evaluation version(called 'lite' or 'student' versions).
  • Most simulation programs that simulate the electronic circuits use a set of algorithms that describe the behaviour of electronic components. The most commonly used algorithm is SPICE (Simulation Program with Integrated Circuit Emphasis).
  • When the circuit design has been completed, with the help of simulation software, it is possible to export a file from the design/simulation software to PCB layout package.
  • It is also possible to export files for use in screen printing or CNC drilling. This greatly reduces the time that it takes to produce a finished electronic circuit.
  • The simulation is like a physical testing. Here the computer model is tested rather than a physical prototype. Like physical testing, simulation is used to validate basic functionality.
  • In addition to that it can be used to gather more date more quickly than is generally the case with a prototype. 

Worst case analysis:

The worst case analysis like sensitive analysis determines whether a system will meet its functional requirements. It is useful to find whether any of the components in the system will get damaged or degraded.

  • The analysis assumes proper equipment usage and no defects in workmanship or components.
  • The wost case analysis is a cost-effective means of screening a design to ensure with a high degree of confidence that potential defects are identified and eliminated prior to production and delivery.

Sensitivity Analysis Tool

The sensitivity analysis tool examines how much each component affects circuit behavior by itself and in comparison to the other components. It also varies all tolerances to create worst case (min & max) measurement values.

  • This analysis is used to identify the sensitive components, then we can optimize(fine tune) the component's values.
  • We can use sensitivity to identify which components affect yield the most, then tighten tolerances of sensitive components and loosen tolerances of non sensitive components. With this information we can evaluate yield versus cost.
  • Sensitivity can with either an absolute value or relative value to a component.

Absolute sensitivity:
Absolute sensitivity is the ratio of change in a measurement value to a one unit positive change in the parameter value.

eg.  There may be a 0.1V change in voltage for a one ohm change in resistance.
Relative sensitivity:
Relative sensitivity is the change in a measurement based on a one percent positive change of a component parameter value.

eg. For each one percent change in resistance, there may be 200 millivolt change in voltage.
Mostly relative sensitivity is used.

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