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Electronic Fundamentals

(202)

Name: Ubayeda Shaqer

Student number: 15975669

Title of the experiment:PSpiceLabratory

Laboratory group:Monday 04:00-06:00

Laboratory supervisor:Barrie Heald

Laboratory partners:Not Applicable

Date performed:12 August 2013

Due date: 26 August 2013

Date submitted: 26 August 2013

I hereby declare that this report is entirely my own work and has not been copied from any

other student or past student.

Student signature: --------------------------------------------------------------


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1.0IntroductionPSPICE is a SPICE analogue circuit and digital logic simulation software that runs on

personal computers. The program is a circuit analysis tool that allows the user to simulate and

analyse a circuit virtually. (e.g.:- extract key voltage and currents)

This first lab is just an introductory that highlights key advantages of using PSPICE for

experiments involving different kinds of circuits.

2.0Aim and objectivesThis experiment is conducted as an introduction to PSPICE. The following tasks were to becarried out:

1. Test Circuits for Transient Analysis.2. Simulation of Op. Amp. Circuits

2.1Low Pass Filter2.2Op. Amp. Based Integrator

3. Simulation of Diode Circuits3.1Diode Bias3.2Diode I-V Characteristic3.3Diode Half-Wave Rectifier Circuit3.4Half-Wave Rectifier Circuit with Filtering


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3.0Theory3.1 Transient Analysis

A transient analysis, also known as time domain circuit, deals with the behaviour of anelectric circuit as a function of time. Since it depends on time, transient analysis uses

different analysis algorithms, control options with different convergence-related issues and

varied initialization parameters than DC analysis.

3.2 Low Pass FilterAn electrical filter is a circuit that modifies the amplitude and phase characteristics of a signal

with respect to frequency. It alters or rejects any unwanted frequencies of an electrical signal.

An example of filters is the low pass filter. A low pass filter passes low frequency signals

while rejecting any signals that have frequency higher than the filters cut-off frequency

(transition occurs). This filter can be formed by combining capacitance, inductance orresistance.

3.3 Op. Amp. Based IntegratorAn integrator operational amplifier is an operational amplifier circuit that carries out

mathematical operation of integration that can cause the output to react to the alteration in the

input voltage over time. The magnitude of the output is determined by the length of time a

voltage is present at its input. In other words, the longer the input is present, the greater the

output becomes.

3.4 Diode V-I CharacteristicA diode is an electronic device allowing current to flow in only one direction. In forward

bias, the diode will not conduct significant current until the voltage reaches about 0.7V. After

that point, the current increases tremendously, causing little change in voltage. Meanwhile, in

reverse bias operation, there is a tiny leakage of current that is negligible. However, if the

maximum reversed voltage of a diode is exceeded, a breakdown will occur. The diode will

fail and current will flow in the opposite direction

Figure 1: The Non-linear Relationship of Current-Voltage


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This relationship is represented in Shockleys equation:

, whereIs= Saturation currentVt= Thermal voltage

When the saturation current,Isis small, the equation can be rewritten as:

In order to obtain a linear current-voltage relationship, a graph of natural log of current versus

voltage is plotted. Shockleys equation then becomes:

ln ln

3.5 Diode Half-Wave Rectifier CircuitThe half wave rectifier is a circuit that converts an AC voltage to DC voltage. By using a

diode, the diode is said to be forward-biased as current flow through it in the positive halfcycle. In the opposite direction, the negative half cycle of the input is eliminated by the one

way conduction of the diode. This means no current flow through and thus the output voltage

is approximately 0V. These are shown in the figure below:

Figure 2: Half Wave Rectification

3.6 Half-Wave Rectifier Circuit with FilteringA basic rectifier converts an ac voltage to a pulsating dc voltage. A filter then eliminates accomponents of thewaveform to produce a nearly constant dc voltage output. All rectifier

circuits by themselves have certain disadvantages:

1. Voltage waveforms have too much variation2. Variation = ripple voltage

Ideally Direct-current supplies should have as little ripple as possible, therefore combined

with a filter will produce a much more efficient system. (e.g.:- parallel capacitor or a series

inductor is also feasible.) The figures below illustrate the advantage of a full wave rectifier

over the half wave rectifier.


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Figure 3: Half wave rectifier with filterFigure 4: Full wave rectifier with filter

4.0MethodThis experiment was carried out entirely using the PSPICE software. Since the test circuits

were all simulated, there is no particular method of carrying out the experiment other than

constructing the test circuits according to the requirements (of values ,parameters and

components).


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5.0ResultsExperiment 1:

The voltage source (V1) is set up by VPULSE with a pulse of height 1 volts, rise time of

50us, fall time of 100us and a pulse width of 1ms and there are two 1k resistors have been

used in this transient analysis circuit.

1.a

Figure 5

1.b

Figure 6

Based on this above simulation, there is no doubt that the output voltage is lower than the

input voltage because the amplitude of input is higher than output and, both the input and

output voltage is completed at every 1ms because of the frequency 1000Hz (time constant

0.001 sec).


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Experiment 2: Low Pass Filter

2.1. a) (demonstration 1)

Figure 7 :DB Scale (blue) for bandwidth (approximately at the 3db point)

Bandwidth Voltage=7.06V

Calculated gain (dc)

Gain

2.1. b) (demonstration 2)

Figure 8


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Experiment 3:Op Amp Based Integrator

2.2. a) (demonstration 3)

Figure 9

Figure 10


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2.2.b) (demonstration 4)

Figure 10


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Experiment 4 :Diodes

3.1 (demonstration 5)

Figure 11

Forward bias

3.2.a) (Demonstration 6)

Figure 12

3.2.b)

IS 2.682000E-09N 1.836


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IV characteristic forward bias

Reverse bias:

3.2.c)

Figure 13


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Experiment 5:Diode Half-Wave Rectifier Circuit

3.3. a)

Figure 14

3.3. b)

Figure 15


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Experiment 6 : Half-Wave Rectifier Circuit with Filtering

3, 4 a)

Figure 16


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Figure 1


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Discussion

1. The first exercise was to stimulate the same series circuit using two different VoltagesourcesVpulse and Vsin input sources.

Observation- Based on the simulation, there is no doubt that the output voltage is lower than

the input voltage because the amplitude of input is higher than output and, both the input and

output voltage is completed at every 1ms because of the frequency 1000Hz (time constant

0.001 sec).

2. Experiment two -stimulate a low pass filter and determine the bandwidth and gain. Observation-Figure 7 illustrates a low pass filter that passes low-frequency signals and cuts

of signals with frequencies higher than the cut-off frequency.

2.1 Bandwidth Voltage=7.06V this was the 3db point taken in from the simulation. This is in

agreement with the theory, where the bandwidth is generally regarded as the

Calculated gain (dc):-

Gain

Time constant from figure 8; 0.2249ms. the bandwidth of the system is the frequency

where |V|^2 drops to half-value, or where = 1. This is the usual bandwidth convention,defined as the frequency range where power drops at most 3 dB.

=0.150ms

The notation f3dB stems from the expression of power in decibels and the observation that

half-power corresponds to a drop in the value of|V|by a factor of 1/2 or by 3 decibels.Thus, the time constant determines the bandwidth of this system.

3. 2.2 There is clear difference between the rises of the second phase of the graph, with100Kohms the second phase is flatter when compared to the 1Kohms graph. This is due to

the increase in the resistance. The time constant in the figure 9 is approximately 1ms.

4. 3.2 IS 2.682000E-09 N 1.836

5. 3.3 ton 12.945 micro seconds Von 0.4V

6. 3.4 ms10. CR

Relative % error of Vr =

9.48%
http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Signal_(electrical_engineering)http://en.wikipedia.org/wiki/Bandwidth_(signal_processing)http://en.wikipedia.org/wiki/Decibelshttp://en.wikipedia.org/wiki/Decibelshttp://en.wikipedia.org/wiki/Bandwidth_(signal_processing)http://en.wikipedia.org/wiki/Signal_(electrical_engineering)http://en.wikipedia.org/wiki/Frequency


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Systematic error when taking down values (Ap) from the graph(simulation) is the main

source of error in this calculation.

discharge curr ent: On the discharge cycle, the maximum current supplied by the capacitor occurs as the output from the rectifier circuit falls tozero. At this point all the current from the circuit is supplied by the capacitor. This is equal to the full current of the circuit.

harging current: On the charge cycle of the smoothing capacitor, the capacitor needs to replace all the lost charge, but it can only achieve this when the voltage from the rectifier exceeds that from the smoothing capacitor. This only occurs over ashort period of the cycle. Consequently the current during this period is much higher. The large the capacitor, the better it reduces the ripple and the shorter the charge period.

AP 4.3152 Vx 4.12 Vr 0.1953 tc 0.142ms T 1.14ms

Average current the through the 10Kohms resistor is 420microAmperes. Charge lost in each

cycle

=386.4 C

Conclusions

References

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