Check By: Dr. Alias Bin Masek Pensyarah Elektronik II Submit: 15 NOVEMBER 2014
TITLE Simple Audio Amplifier
AIM To improve our knowledge about the operation of audio amplifier circuit.
To understand the function of circuit.
To understand about the application of transistor in audio amplifier circuit.
To make the connection of audio amplifier circuit based on schematic circuit.
To get the output of the audio amplifier circuit.
Stand of soldering
Set of hand tools
Resistor 1K Ohm
Resistor 100K Ohm
Figure 1: Audio Amplifier Circuit
Prepared all the equipment and component follow by lab sheet.
Based on circuit in figure 1 given, make the connection on the Vero Board.
Defined the emitter, collector and based of the transistors using by multimeter.
After that, solder the components of circuit using by soldering iron.
Be carefully when we are using the soldering iron.
Test circuit using a multimeter if the connection is right or wrong.
Then, applied the power supply 9V and Audio In from radio.
If the audio circuit in a good condition it must have the output. The output is the same like the sound of radio.
Overall, audio amplifier circuit that I created Connection is successful and it is supposed to sound. However, the output sound is not too loud because the speakers are not suitable. We should use 25 Ohm speaker to get a good result.
DISCUSSION OR ANALYSIS
Some knowledge about the experiment:
Figure 2 : Audio Amplifier Circuit Description of circuit
This is the circuit diagram of a simple three transistor audio amplifier that can deliver around 100mW power to a 25 Ohm speaker.
The diodes D1 and D2 provide a constant bias voltage for the transistors Q1 and Q2.
The transistor Q1 works as a preamplifier.
Transistors Q2 and Q3 drives the speaker.
The type no of the transistor is not very crucial here.
You can use any NPN transistor for Q1, Q3 and any PNP transistor for Q2.
Any way the minimum collector current capacity of the transistors must not be less than 100mA.
The circuit will work well with an 8 ohm speaker too, but the volume will be a little less.
The function of the component of circuit: This is the function of the component that we are using for this experiment.
NO. COMPONENT 1.
Diode is a two-terminal electronic component with asymmetric conductance, it has low (ideally zero) resistance to current in one direction, and high (ideally infinite) resistance in the other.
The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction), while blocking current in the opposite direction (the reverse direction).
A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a P–N junction connected to two electrical terminals.
A vacuum tube diode has two electrodes, a plate (anode) and a heated cathode.
Semiconductor diodes were the first semiconductor electronic devices.
A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power.
It is composed of semiconductor material with at least three terminals for connection to an external circuit.
A voltage or current applied to one pair of the transistor's terminals changes the current through
another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal.
Some transistors are packaged individually, but many more are found embedded in integrated circuits.
A device which converts an electrical audio signal into a corresponding sound.
Produce audio output that can be heard by the listener.
Capacitors are components that are used to store an electrical charge and are used in timer circuits.
A capacitor may be used with a resistor to produce a timer. Sometimes capacitors are used to smooth a current in a circuit as they can prevent false triggering of other components such as relays.
When power is supplied to a circuit that includes a capacitor - the capacitor charges up. When power is turned off the capacitor discharges its electrical charge slowly.
Poser supply for the circuit
Based on the experiment we understand about the function of audio amplifier circuit, where this device will produce of sound. After that, we can understand about the application of transistor in audio amplifier circuit. Overall the function of transistor Q1 works as a preamplifier and the transistor Q2 and Q3 as a drives the speaker. Other than that, we can apply our skill in soldering component on the board. Lastly, I’m get the best output from this experiment.
EXPERIMENT ACTICITY (PICTURE)
Figure 1: The Equipment that using for this experiment
Figure 2: Multimeter for defined the leg of transistor and test the circuit
Figure 3: Soldering process
Figure 4: Soldering process and cut the component’s leg
Figure 5: Complete circuit
Figure 6: Testing the project to get the output using by audio system from radio and computer.