Measurement & Evaluation of Audio Amplifier Circuit Assignment PDF

Measurement & Evaluation of Audio Amplifier
Circuit using LM386
1. Introduction
1.1 Aim:
The aim of the study is to construct an audio amplifier circuit using IC, LM 386.The built
circuit can be used in low voltage consumer devices. Orcad Capture software is used to
build the schematic of the amplifier. PSpice is used to measure and evaluate the
frequency response and waveforms of the circuit in three different domains which are:
a) AC Sweep
b) Transient ( Time Domain)
c) Time Domain ( Transient)
1.2Applications
An audio amplifier is used to produce the sound output out of all devices. The
audio amplifier are used in various devices which includes[ CITATION Ele20 \l
1033 ]:
a) Home audio systems
b) TV sound systems
c) Intercom
d) Portable MP3 players
e) Radio
f) Robots
g) Acoustic Weapons
h) Ultrasonic/Small servo/Line Drivers
i) Power Converters
1.3 Background
1.3.1 LM386 Audio Amplifier:
A device used to amplify (increase) the amplitude of a low power audio signal
is known as amplifier. The output of signal is measured in volts or amperes.
Signals are merely composed of frequencies with in the human hearing range
i.e. 20Hz to 20,000 Hz. The low voltage audio amplifier, LM386 IC gain is 20

dB, that can be increased to any value within the range of 20 and 200 dB by
basically inserting an external series Resistance/capacitance circuit between
gain controlling pin i.e. pin 1 and pin 8 of the IC. The increase in AC power is
from the i/p terminals to the o/p terminals is due to the biasing of the circuit
provided by the DC voltage source. LM386 pin 2 & pin 3 are the inverting and
non-inverting inputs of the amplifier. Pin 2 is always connected to the ground.
The output pin is pin 5. Pin 7 sets the path of decoupling whereas pin 6 and
pin 4 are the used to supply the power to IC LM386. A 9v power supply is
used in construction the audio amplifier circuit[ CITATION Dou \l 1033 ].
Figure 1 Pin Diagram of LM386
1.3.2Types of Audio Amplifier Circuits:
Amplifiers are categorized according to their input & output parameters.
Various types of amplifier circuits are described as follows[ CITATION Vim17 \l
1033 ][ CITATION Elp20 \l 1033 ]:
a) Audio frequency amplifier : A type of amplifier used to amplify audio
frequencies up to 100 kHz. Loudspeakers are driven by the power
provided by audio frequency amplifier.
b) Midway frequency amplifier: A tuned amp whose aim is to amplify
the voltage of the signals of TV/Radar, before the audio or video
information carried by the signal is separated or demodulated from the

radio signal. The frequency at which the amplifier operates is intermediate
frequency.
c) Radio frequency amplifiers: A tuned amplifier used to increase the
power of low-frequency radio signal. The tuning of the circuit can be
adjusted depending on the amplifier purpose.
d) Ultrasonic Amplifiers: An amplifier which amplify the ultrasonic waves
from 20 kHz up to about 100 kHz. Ultrasonic cleaning & ultrasound
scanning can be performed using ultrasonic amplifier.
e) Wideband Amplifiers: It amplifies a band of frequencies up to several
tens of MHZ. Measurement of signals spreading over a wide range of
frequencies is performed through this amplifier.
f) Direct Coupled Amplifiers: A type of amplifier used to amplify very low
frequency signals. It is used to amplify DC i.e. zero frequency. It is widely
used in measuring instruments & control systems.
g) Video Amplifiers: A wide band amplifier used to improve the signals of
the video and display it with high resolution.
h) Buffer Amplifiers: It is used for the transformation of electrical
impedance from one circuit to another.
i) Operational Amplifiers: A type of voltage amplifier used to perform
mathematical operations on voltages such as addition subtraction etc.
1.4 OrCAD Software Types & Features
OrCAD a widely known software used for designing and simulation of electronic
circuits. The software also has options of PCB designing and analysis of
electronic circuits. The applications of software are as follows[ CITATION Orc20
\l 1033 ]:
a) OrCAD Capture (CIS): An application used to draw a schematic of the circuit
using a variety of provided circuit symbols. It can also export the schematic
to other circuit board designers.
b) PSpice: A simulation software used to simulate and analyze the captured
circuit. It is also used for the verification of analog and mixed-signal circuits
and supports the following categories of analyses: