report electronic circuit 1 audio amplifier

Instructor: PhD Nguyen Vu Thang Student’s name: Pham Viet Hoang Student’s ID: 20182951AUDIO AMPLIFIER REPORT:- -----SCHOOL OF ELECTRONIC AND TELECOMUNICATION... List of figures:Figure 1:

Instructor: PhD Nguyen Vu Thang Student’s name: Pham Viet Hoang

Student’s ID: 20182951

AUDIO AMPLIFIER REPORT:

- -

SCHOOL OF ELECTRONIC AND TELECOMUNICATION

4.2 Stage 1: Voltage amplifier 7

4.3 Stage 2: Current amplifier 10

4.4 Stage 3: Power amplifier 15

List of figures:

Figure 1: Block

Figure 2: Audio- amplifying circuit sketch………7

Figure 3: Voltage- amplifying circuit sketch………8

Figure 4: Current- amplifying circuit sketch………9

Figure 5: Power- amplifying circuit sketch……… 10

Figure 6: Circuit simulation on the Proteus software………11

Figure 7: Simulating result on Oscilloscope……….11

1 Introduction

In term 2021.1,I learn about amplifiers and transistors, and now,I design the audio amplifier circuit using BJT for more understanding about its operation and its application.

Non-functional requirements:

Simple, easy to use Easy to fix Low cost • Compact size

2.2 Description

The audio power amplifier, also known as the audio amplifier, is a type of electronic amplifier that amplifies low-power audio impulses to a level sufficient for driving loudspeakers (the frequencies of low-power signals are always between20Hz and 20KHz, which is the range of human hearing) A three-stage circuit mustbe designed to build a full circuit for the audio power amplifier.

2.3 Parameters

Power supply: 15VDC

Input signal: 100mV AC (The signal is supplied through the audio jack from our computer or smartphone).

Efficiency: Frequency response: Frequency response is the term used to describe the range of tones that a stereo system can reproduce The range of frequency response should be wide enough (20Hz to 20 KHz) The frequency response should be flat (linear)

Amplifier gain: Combination of the pre-amplifier’s gain and the amplifier

power-3 Block diagram

Our product is divided into 6 main parts: AC input signal, Power supply, Voltage amplifier, Current amplifier, Power amplifier and Speaker or Load

Figure 1: Block

4 Block designing

4.1 Circuit sketch

We use:

• The NPN transistor, BC547 to amplify the small input signal because it is used asa small signal transistor for VHF (very high frequency) amplifier.

• TIP41C, TIP42C to amplify the power of signal because they are power BJT

4.2 Stage 1: Voltage amplifier

We employ the Common-Emitter voltage-divider bias setup in the voltage amplifier circuit The voltage-divider bias setup is less affected by temperature changes, which is why it is more stable than other biasing systems The voltage gain is increased by using the bypass capacitor.

Figure 2: Audio- amplifying

DC Mode:

Figure 3: Voltage- amplifying

- Based on the data sheet of BC547, choose:+ The working point of Q is: = 6V ; = 12.5mA+ = 250

- Apply Kirchoff’s voltage law: = + + +

+ + = = = 720

Since + is the emitter voltage at Q point.Choose: + = = 120 = 720 – 120 = 600 In reality: Choose = = 300 - = = 2.08

- Assume = 45

= 45 => = 45 = 11.25

= 11

- + = 120 => = 109 =110

= 91.2 = 91

- Since << => The circuit is stable << (+ ) = 250 x 120 = 30000 = = 3k

- Apply Kirchoff’s voltage law: = + + +

= x + 0.7V + 1.5V = 16.34k

= 16k ; = 330

AC Mode:

- = // // ( + ) = 16.34k // // 250x(2.08 + 11 ) = 1427.87

- =

= 600 - = 5.6

Choose = 100 - Similarly, choose = 100 Current of the output signal:- = =

= 0.07 mA-

=

15992

4.3 Stage 2: Current amplifier

I choose emitter – follower Darlington connection configuration to amplifier the current Stage 1 does not amplify the current so much At this configuration, the voltage gain is always approximately 1 I want to use this circuit to amplifier the small current with high gain to increase the Power.

= = 0.07 mA

- Stage 2 need to amplify to the value of Current gain of stage 2 is:

= = = 640

- does not amplify the voltage, so assume that = 1 =

= = 38.53 k Choose = 39 k

DC MODE:

Figure 4: Current- amplifying

Because the output current of this stage will cause important effect on stage 3 (namely heat effect on T4 & T5), so based on the datasheet of TIP41, I choose the working point of T3 is ( = 6V, = 0.25A) At that point = 55

= - = 15 – 6 = 9V

- From the operation point of , assume that = 0.73V = 0.25 A

= = = 4.55 mA = = 4.55 mA

- With = 4.55 mA, based on the datasheet of BC547, choose = 110.- Similarly, assume = 0.7V

= = = 41 -

= + + + = = = 111.46 k = 112 k = =

= 36

AC MODE:

= = = 0.1

= // (// ) = 112 k // [110 x 55 x (36 // 60.2 )] = 61.5 k ( > = 39 k )

= 0.1 = = 0.13 Choose = 100

4.4 Stage 3: Power amplifier

The output stage of a Class AB amplifier combines the benefits of both a Class A and a Class B amplifier while reducing the drawbacks of each, such as low efficiency and distortion It outperforms class A and has less distortion than class B I employ a pair of normal forward biased diodes within the amplifier's biasing configuration to correct for any temperature-related change in the base-emitter voltage (VBE), as illustrated below.

- The output device is an 4 – 3W speaker.

- To avoid damage the equipment, we have: = 4 , = = 2.5W

= = V

= = 3.16V x 4.5 VThe input voltage is 100mV

The maximum voltage gain of the system is: = =

= 45

- avoid signal distortion, choose 2 = 2 x 4.5 = 9V

Figure 5: Power- amplifying

= 15V = = = 1.12 A

- Based on the datasheet of TIP41 and TIP 42, assume that = = 50 = = = = 22.4mA

Apply Kirchoff’s voltage law: = + + +

+ = - - = 15V – 0.7V – 0.7V = 13.6V= = = 6.8V

= = = = 303.57 = = 300 = 1.99

Choose = 2.2 mF = = = 0.023

Consider one half of this stage:

= // ( + ) = 300 // 50x(0.023 + 4 = 120.41 = = 60.2

= 0.023

Input current for this stage to get the maximum power of the speaker: = = 1 = 30.1

= = = = 37.2 mA = + = 22.4mA + 22.4mA

= 44.8 mA = = = 66

Figure 6: Circuit- Simulation on the

5.2 Simulating result

6.Testing with breadboard

7.Layout PCB circuit

On the breadboard, the output sound is audible, however TIP41 and TIP42 are extremely hot.I learned how to construct electronic circuits and run simulations as a result of this assignment I may have made a mistake during the procedure, and I am hoping that the teacher can assist me in correcting it Thank you so much for everything.