Ecd302 unit 04 (analysis)
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This document provides an overview of various analysis tools available in EWB software for circuit simulation and analysis. It describes the following analysis types: DC operating point analysis, AC frequency analysis, transient analysis, Fourier analysis, noise analysis, distortion analysis, DC sweep analysis, sensitivity analysis, parameter sweep analysis, temperature sweep analysis, transfer function analysis, worst case analysis, pole zero analysis, and Monte Carlo analysis. For each analysis type, it provides a brief description of the analysis and an example circuit to demonstrate how to set up and interpret the results of that analysis.
Ecd302 unit 04 (analysis)
- 2. Analysis Tools • Three major types of analysis: – DC analysis – AC analysis – Transient analysis
- 3. A Quick Tour of the Analysis EWB does this… When you choose… DC Analysis AC Analysis Transient DC Operating Point Yes AC Frequency 1st 2nd Transient 1st 2nd Fourier Yes Noise 1st 2nd Distortion 1st 2nd Parameter Sweep Optional Sweep Optional Sweep Optional Sweep Temperature Sweep Optional Sweep Optional Sweep Optional Sweep
- 4. A Quick Tour of the Analysis EWB does this… When you choose… DC Analysis AC Analysis Transient Pole Zero Yes Transfer Function Yes DC Sensitive Yes AC Sensitive 1st 2nd Monte Carlo Optional Optional Optional Worst Case Optional Optional Optional
- 5. DC Operating Point Analysis • To determines the DC operating point of a circuit. • Results are DC node voltages and branch currents. Setting for DC analysis: – AC sources are zeroed out. – Steady state is assumed: • Capacitors are open circuits. • Inductors are short circuits. – Assumptions: Digital components (such as IC’s) are treated as large resistances to ground.
- 7. Setting DC Operating Point analysis parameters • There is no analysis parameters to be set. • User able to select which voltages or branches to analyze. Available voltage nodes Available Current branches Selected variable for analysis
- 8. DC Operating Point analysis result Volt Ampere Direct measurement to the original circuit would not obtain these results.
- 9. Example: Colpitts Oscillator When running DC Operating Point Analysis, Multisim reduces the circuit like below: Output voltage Collector Current
- 10. AC Frequency Analysis • To determines how the circuit behave to a range of frequency. Setting for AC analysis: • The DC operating point is first obtained for non-linear circuit. • All input sources are considered to be sinusoidal. • The frequency of the sources is ignored. • The AC simulation is done based on a sweep over a range of frequencies.
- 11. AC Frequency Analysis • Assumptions: Analogue circuits, small signal. Digital components are treated as large resistances to ground. • The result is displayed on two graphs: – Gain versus Frequency – Phase versus Frequency Similar to using Bode Plotter for measurement
- 12. Example: 5V DC power supply
- 13. Setting AC frequency analysis parameters
- 14. Result What can you comment for this frequency range? Is this a distortion? Gain versus frequency Phase versus frequency
- 15. Transient Analysis • Also called Time-domain analysis. • Closely simulates the phenomena seen in the real circuit by means of an oscilloscope. • To determines how the circuit behave over time. • A simulation consists usually of a time sweep starting at time, t = 0. • The result of the transient analysis is a graph of voltage versus time.
- 17. Setting Transient analysis parameters
- 18. Result Input voltage signal (Vin) Output voltage signal (Vout) What can you comment on the circuit response time?
- 19. Fourier Analysis • A method to analyze complex periodic waveforms. • It permits any complex periodic waveforms to be resolved into sine or cosine waves and a DC component. • This permits further analysis and allows you to determine the effect of combining the waveform with other signals.
- 20. Fourier Analysis • The Fourier analysis is basically the same as spectrum analyzer. • The only difference is, the spectrum analyzer runs continuously, reflecting any changes in the harmonics of the input waveform, whereas the Fourier analysis performs the analysis only within a specified period of time.
- 21. Setting • Do not worry about setting the frequency resolution. When not sure what to do, just press the “estimate” button to have the software estimate for you.
- 22. Estimate • The software estimated the fundamental frequency of our complex waveform to be 5 kHz. • Isn’t our lowest frequency 10 kHz? Well, yes, but that is not the fundamental frequency. The fundamental frequency should be the lowest common factor of all the frequencies. In this case, precisely 5 kHz.
- 23. Number of harmonics • In our case, we need at least 10 harmonics to show the 50 kHz harmonic. (Our fundamental is 5 kHz, so 50 kHz is the 10th harmonic.) But we will set the number of harmonic to 20, assuming we do not know the answer.
- 24. Stopping time • As mentioned before, fourier analysis is only performed for a fixed period of time. So, we need to specify that period of time as well. Let us make our setting as 0.01 s:
- 25. Specifying output • You need to also specify the output node of your circuit. In this case, node 5.
- 26. Results of Fourier analysis: Need to scroll down to show the third component (which is the 10th harmonic)
- 27. Noise Analysis • Noise is any undesired voltage or current appearing in the output. • One common result of noise is “snowy” television reception caused by fluctuations across all frequencies of TV signal. • Multisim can model 3 kinds of noise: – Thermal noise – Shot noise – Flicker noise
- 28. Noise Analysis • Thermal noise – Is temperature dependent and caused by the thermal interaction between free electrons and vibrating ions in a conductor. – Its frequency content is spread equally throughout the spectrum.
- 29. Noise Analysis • Shot noise – Cause by the discrete-particle nature of the current carriers in all forms of semiconductors. – The major cause of transistor noise. – The equation for shot noise in a diode is given as below. – For other devices such as transistors, no valid formula is available. Provided in manufacturer’s data sheet.
- 30. Noise Analysis • Flicker noise – Also known as excess noise, pink noise or 1/f noise. – Present in BJT and FET and occurs at frequencies below 1kHz. – It is inversely proportional to frequency and directly proportional to temperature and DC current levels.
- 32. Setting Noise analysis parameters
- 33. Result The thermal noise voltage produce by resistor R1 The thermal noise voltage produce by resistor R2
- 34. Distortion Analysis • Distortion analysis is a type of transient analysis that applies a single frequency sinusoidal signal to the input source and measures the resulting distortion in the specified output. • Signal distortions are usually the result of gain non linearity or phase non uniformity in a circuit. Nonlinear gain causes harmonic distortion, while non uniform phase causes inter modulation distortion. • Distortion analysis is useful for investigating small amounts of distortion that are normally un-resolvable in transient analysis.
- 35. Example: Class B push-pull amplifier
- 36. Setting Distortion analysis parameters
- 37. Result
- 38. DC sweep analysis • To quickly determines the DC operating point of your circuit by simulating it across a range of values for 1 or 2 DC sources. • The effect is the same as simulating the circuit using DC operating point analysis several times with different values.
- 40. Setting DC sweep analysis parameters
- 41. Result The collector voltage versus the collector source
- 42. Sensitivity analysis (DC and AC) • Sensitivity analysis help to identify the components which affect a circuit’s DC bias point the most. • This will focus efforts on reducing the sensitivity of the circuit to component variations (or drifting). • It may provide evidence that a design is too conservative and that less expensive components, with more variation may be used.
- 44. Setting sensitivity analysis parameters
- 45. Result Changes to resistor, R2 affect the circuit output for over a range of frequency
- 46. Parameter Sweep Analysis • A function that able to perform 3 types of sweeps: – DC operating point analysis – Transient analysis – AC frequency analysis • You will find that some components have more parameters to perform a sweep. While others, such as inductors has only inductance available as a parameter for analysis.
- 48. Setting parameter sweep analysis parameters
- 49. Result
- 50. Temperature Sweep Analysis • Quick verification of circuit behaviour towards temperature changes. • Similar to simulating the circuit several times, once for each different temperature. • Default temperature is 27°C. • Default temperature may be changed from the Analysis Options’ Global tab.
- 52. Setting temperature sweep analysis parameters Default temperatureSweep parameter
- 53. Result
- 54. Transfer function analysis • Transfer function analysis calculates the DC small-signal transfer function between an input source and two output nodes (for voltage) or an output variable (for current) in a circuit. • It also calculates input and output resistances.
- 56. Setting transfer function analysis parameters
- 57. Result
- 58. Worst case analysis • Worst case analysis is a statistical analysis that lets you explore the worst possible effects of variations in component parameters on the performance of a circuit.
- 60. Setting Worst case analysis parameters
- 61. Result
- 62. Pole Zero Analysis • Finds the poles and zeros in the small-signal AC transfer function of a circuit. • Useful in determining the stability of electronic circuits. Stable circuits should have poles on negative real parts. • Note: May occasionally receive message such as: “Pole-zero iteration limit reached, giving up after 200 iteration” Even with this message, the analysis may still have found all the poles and zeros.
- 63. Example: LR passive filter
- 64. Setting Pole Zero analysis parameters
- 65. Result
- 66. Monte Carlo Analyses • Statistical analysis that allows explorations in affects brought by component properties variations. • The first simulation is always performed with nominal values. • For the rest of the simulations, a delta value is randomly added to or subtracted from the nominal value. • The tolerance percentage is applied globally.
- 68. Setting Monte Carlo analysis parameters
- 69. Result