Programme: HND Electrical & Electronic Engineering

Unit Number and Name: Unit 66 Electrical, Electronic and Digital Principles T/601/1395

Level: QCF Level 5

Assignment Title - Amplifier Circuits

TASK INTRODUCTION

You are an electronics design engineer. You have been asked by your manager, Dave, to analyse single stage and two stage amplifier circuits and to document your findings in a technical report

TASK 1:

Part 1
Using simulation software (Multisim), build the Class A audio amplifier circuit, with an input ( 1mV (p-p) 12kHz.
a) Measure the voltage gain of the amplifier with 8ohm load
b) Measure the voltage gain of the amplifier without a load
c) Calculate the input impedance.
d) Measure is the input impedance.

Part 2

Using simulation software (Multisim), build a 2 stage Class A amplifier circuit using the amplifier circuit from Part 1 and adding a second transistor amplifier connecting the output of the first amplifier circuit to the input of the second amplifier circuit.

a) Measure the voltage gain of the amplifier.
b) Measure the power gain of the circuit.

TASK 2:

Part 1

Create a table showing the load/ non-load output values of the single stage and compare them with the two stage amplifier output values.

Which amplifier gives the most power output into a Bohm (speaker) load?

Part 2

Explain why the amplifier you chose in part 1 is the best for driving a speaker of 8ohms. Opportunity for Merit

Research Single and Two-Stage Class A and class B amplifiers. and include and explanation about which type amplifier is the most efficient.

Opportunity for Merit

Create a MS PowerPoint presentation about single and two-stage amplifiers and present it to the group (5 minutes).

TASK 3:

For this task, you have been tasked with the design of a simple Class A amplifier which will provide a 1kHz sine wave signal to the following specification:

a) Show your design with all calculations for R1, R2. C1, C2, RC. RE.

b) Using simulation software (Multisim), evaluate your design against the specification required. You are required to tabulate the results obtained and provide annotated record of the input and output waveforms.

TASK 4:

a) From the circuit designed and simulated in TASK 3 above. build the actual designed circuit and using lab instruments. confirm the design conforms to the original specifications,

b) Demonstrate your circuit to the lecturer.

c) Discuss your findings, highlighting any differences found between your theoretical design (simulated) and physical (actual) design produced

Opportunity for Distinction

Discuss how the circuit for TASK 4 can be extended to show how the design can be altered to increase the ac signal gain by a factor of 2 at a frequency of 10kHz.

TASK 4:

Actual circuit is built using the lab equipment and tested. We have following table as output values being measured in the lab:

Table 2: Hardware implementation output data measurement

Vb

IE                    : lc

Vout

Gain (Av)

0.9

6.02 mA

7.2 mA

8.43

8.5

Hence, our circuit in real time is also working as per simulated results. The only difference is due to the internal losses and change in current gain due to temperature increase. Also practical circuit is exposed to disturbances like noise and other electrical noise addition, which in turn adds non-linearity in the circuit.

Gain can be increased by adding feedback capacitor to emitter resistor RE, it will cause voltage to appear at the input or base of the transistor which in turn increases the overall gain of the amplifier. Negative feedback resistor may also be added to increase the gain,

Av = ~Rc/RE = -10, so by reducing RE =RE/2 would increase the gain by a factor of 2.

Hence, replace RE = 15 ohm gives us gain of 2Av as previous.

Conclusion

In this project we have implemented single stage class-A amplifier with and without loads. As the number of stages is increased power gain increases. Class-A amplifiers can be employed for voltage as well as current gain circuits. Design of common emitter amplifier is done and simulated using MULTISIM simulation. Hardware implementation is done while analyzing the circuit on MULTISIM. We can conclude that our circuit or amplifier designed have high input impedance, low output impedance, high voltage
gain and current gain along with power gain to drive the 8 ohm speaker load.

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Part 1

Case 1 : With load:

Vin= 743.58 uV, Vo=44.715 uV

If Vin = 558.83 uV, Iin = 63.288 nA, Vo=33.784 uV

a)      Voltage gain = Vo/Vin = 44.715/743.58 = 0.06

c)Calculation (Input Impedance) = 220k||30k||(B+1)re = 9 k Ohms

d)Input Impedance = Vin/Iin = 558.83*1000/63.288=8.83k Ohms

Circuit:

Waveforms:

Case 2 : No load

b)      Voltage Gain = Vo/Vin =  90/1 = 90 from graph

Part 2:

Vin = 476.37 uV, Iin=54.632 nA, Vo=2.7165mV, io=339.56 uA

a)      Voltage Gain = Vo/Vin = 5.7

b)      Power Gain = Vo*Io/Vin*Iin =( 2.7165*339.56/476.37*54.632 ) *10^6

= 35443 = 45.5 dB

Circuit:

Waveforms: