Reference no: EM133073973
M21388 Introduction to Analogue Circuits - University of Portsmouth
Ultrasonic Signal Amplifier
Assessment
Section 1 - Investigation of Analogue Circuits
Experiment 1: Verification of Circuit Analysis Methods
The purpose of this experiment is to verify the classical circuit analysis approaches, which include the mesh analysis method and the nodal analysis method, using the LTspice simulator.
Tasks for Experiment 1:
(1) Write the mesh current equations and determine the value of the mesh currents. Theoretically calculate the current through and the voltage across each resistor.
(2) Write the nodal voltage equations and determine the value of the nodal voltages. Theoretically calculate the current through and the voltage across each resistor.
(3) Build up the circuit in the LTspice simulator and complete the simulation analysis; capture the waveforms of the current through and the voltage across each resistor.
(4) Compare the theoretical prediction with the simulation results.
Evidence required in your report for the assessment of Experiment 1:
• Title of your investigation.
• Description of your investigation (what did you do).
• The full working of determining the voltages across and the currents through each resistor, respectively using the mesh analysis and the nodal analysis methods should be presented. You can write down your working on a piece of paper and include the photo of the working in your coursework report.
• A circuit diagram built up in the LTspice simulator.
• Captured waveforms labelled with all relevant parameters.
• Investigate the difference in the results obtained using the mesh analysis method, the nodal analysis method and the simulator. Discuss the results. This must fully explain your findings.
• Full source files ready for simulation (submitted along with the report).
Experiment 2: Verification of the Thevenin's Theorem
The purpose of this experiment is to verify Thevenin's theorem, using the LTspice simulator. Thevenin's theorem can significantly simplify the analysis of a circuit and thus has been widely used in practice. The most important steps of obtaining the Thevenin's equivalent circuit of an analogue circuit are the determination of the Thevenin's equivalent voltage ETh and the Thevenin's equivalent resistance RTh.
Tasks for Experiment:
(1) Determine the Thevenin's equivalent voltage ETh and the Thevenin's equivalent resistance RTh external to R5.
(2) Draw the Thevenin's equivalent circuit external to R5.
(3) Choose a random resistance value for R5 and theoretically calculate the current through and the voltage across R5.
(4) Using the chosen value of R5, build up the circuit in the LTspice simulator and measure ETh and RTh external to R5.
(5) Capture the waveforms of the current through and the voltage across R5.
(6) Compare the theoretical prediction with the simulation results.
Evidence required in your report for the assessment of Experiment 2:
• Title of your investigation.
• Description of your investigation (what did you do).
• The full working of determining ETh and RTh external to R5. You can write down your working on a piece of paper and include the photo of your working in the coursework report.
• Theoretical prediction of the voltage across and the current through R5.
• A circuit diagram built up in the LTspice simulator.
• Measurements of ETh and RTh in the LTspice simulator.
• Captured waveforms labelled with all relevant parameters.
• Investigate the difference between the theoretical prediction and the simulation results. Discuss the results. This must fully explain your findings.
• Full source files ready for simulation (submitted along with the report).
Experiment 3: Common-collector Amplifier (Emitter Follower)
The purpose of this experiment is to introduce basic configurations of the emitter follower circuit. Emitter followers are used to buffer signals, which means they are capable of taking a signal from a high impedance source and delivering it to a low impedance load.
An example of a simple emitter follower is shown in Fig. 3, where dual DC voltage sources are utilised. In this circuit, the input signal is a 1 kHz sinusoidal wave with an amplitude of 1 V. You should find and read the datasheet of the transistor 2N3904 before building the circuit.
A properly biased emitter follower circuit, operating from a single positive supply is shown in Fig.4. In this circuit, the input signal is a 1 kHz sinusoidal wave with an amplitude of 2 V. The analysis of a similar circuit can be found on pages 70-71 of the recommended book, "The Art of Electronics" second edition, by Horowitz and Hill, published by Cambridge University Press. The purpose of this experiment is to familiarise you with the concept of biasing a transistor so that it is always in its operating region.
Tasks for Experiment 3:
1. Choose a random load resistor (whose value is greater than 10 k?) to connect between the output and the ground to serve as a load for the circuit. Build up the circuits shown in Figs. 3 and 4 (including the load resistor), using the LTspice simulator.
2. Compare the input voltage signal with the output voltage signal and find out whether there are any changes in the magnitude and in the phase.
3. Compare the input current signal with the output current signal and find out whether there are any changes in the magnitude and in the phase.
4. Determine the voltage gain and the current gain of the circuits.
5. Determine whether the output power is increased.
6. Compare Fig.3 and Fig. 4 and comment on the advantages and the disadvantages of the circuits.
7. Capture the waveforms of the input signal (the output of the function generator) and the output signal of the circuits.
Evidence required in your report for the assessment of Experiment 3
• Title of your investigation
• Description of your investigation (what did you do)
• Circuit diagrams
• Captured waveforms labelled with all relevant parameters
• Discussion of results. This must fully explain your findings
• Full source files ready for simulation (submitted along with the report).
Experiment 4: Common-Emitter Amplifier
A common-emitter amplifier is shown in Fig. 5. In this circuit, the input signal is a 1 kHz sinusoidal wave with an amplitude of 0.2 V. Unlike the emitter follower, this amplifier is capable of producing an output voltage that is larger than the input. This circuit fulfils the requirement to bias the transistor so it can pass positive and negative signals but without the need for a negative power supply. It also provides an amplifier with a voltage gain that is independent of the value of hFE.
The learning objective of this experiment is to reinforce the theory taught in lectures on transistors and DC circuit theory.
Tasks for Experiment 4:
1. Calculate the quiescent values of: VB, VE, IE, IC and VC (to calculate the quiescent operating points, the input signal source is disconnected from the circuit).
2. Choose a random load resistor (whose value is greater than 10 k?) to connect between the output
and the ground to serve as a load for the circuit.
3. Calculate the theoretical AC voltage gain of the circuit.
4. Build up the circuits shown in Fig. 5 (including the chosen load resistor), using the LTspice simulator.
5. Capture the waveforms of the input signal and the output signal of the circuits;
6. Compare the input voltage signal with the output voltage signal and find out whether there are any changes in the magnitude and the phase.
7. Compare the input current signal with the output current signal and find out whether there are any changes in the magnitude and the phase.
8. Measure the AC voltage gain and the AC current gain of the circuits.
9. Determine whether the output power is increased.
10. Compare the theoretically predicted AC voltage gain with the one measured through simulation.
11. Change the frequency of the input signal. Measure the voltage gain at 10 Hz, 100 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz, 10 MHz and 100 MHz. Observe the changes in the voltage gain and explain the reasons for the changes.
Evidence required in your report for the assessment of Experiment 4
• Title of your investigation
• Description of your investigation (what did you do)
• Circuit diagram
• Captured waveforms labelled with all relevant parameters
• Discussion of results. This must fully explain your findings
• Full source files ready for simulation (submitted along with the report).
Section 2 - Project to Design an Ultrasonic Signal Amplifier
Specification and requirements
• The peak-to-peak amplitude of the ultrasonic signal is 10 mVP-P, and the resistance (internal
resistance) of the ultrasonic transducer is 500 ?.
• The peak-to-peak amplitude of the output signal is between 4 VP-P and 5 VP-P.
• A 1 M? resistor (the load) is connected between the output stage of the amplifier and the ground.
• The waveform of the output signal is not distorted.
• Operates from a 15 V DC voltage supply.
Attachment:- Introduction to Analogue Circuits.rar