In the previous tutorial, working principle and classification of microphones was discussed. The microphone is an input transducer which converts sound waves into electrical signals. The audio signals from a MIC are amplified by a preamplifier and transferred to the main audio unit. The audio unit might comprise of amplifier and/or filter circuit or may have other circuitry to store audio to a computer. The amplified or stored audio is reproduced using another type of transducer which is called speaker. The Speaker is a type of output transducer which converts the electrical signal into audio signal. Speakers are enclosed in a rectangular or square shape cabinet. The shape of the box affects the quality of the sound. The cabinet consists of different types of transducers/speakers which produce different types of audio frequency. Each transducer is called as ‘driver’ and the whole cabinet is known as ‘loudspeaker’.
In the previous tutorials, physical properties of sound waves and acoustic waves were discussed. Sound or Acoustic Waves are in the form of vibration. Sound needs to be converted into electrical signals so that it can be processed by electronic circuits. So, the sound which is a mechanical energy must convert into electrical energy and must be precisely represented as an electrical waveform (analog) for any signal processing operations. So, there is need of a device which could sense the audio signals efficiently and convert them into electrical signals.
The audio electronics is a branch of electronics that deals with designing of circuits that convert sound into electrical signals or electrical signals back into the sound. These circuits all together form an audio system. Basically, an audio system is designed to receive audio signals (via microphone), record audio in some storage, transmit audio (through wired or wireless communication channels) and reproduce audio signals (via speakers). So, the audio circuits perform signal processing for representing the sound in the form of electrical signals, manipulate the electrical (audio) signals like amplifying, filtering or mixing, reproduce sound from the audio signals, store audio into computer files or reproduce audio from an audio file. All these processes are performed by different audio related circuits or devices.
In the previous tutorials, two of the most important building blocks of an audio system – Microphone and Speaker were discussed. An audio system is designed to receive audio signals (via microphone), record audio in some storage, transmit audio (through wired or wireless communication channels) and reproduce audio signals (via speakers). So, the audio circuits perform signal processing for representing the sound in the form of electrical signals, manipulate the electrical (audio) signals like amplifying, filtering or mixing, reproduce sound from the audio signals, store audio into computer files or reproduce audio from an audio file.
In the previous tutorial, sound wave and its properties were discussed. Now it’s time to understand Acoustic Waves. Generally, the term sound wave is used to refer the waves having frequency range audible to humans that is 20 Hz to 20 KHz. The waves having frequency greater than 20 KHz are called Ultrasonic waves and waves having a frequency range in Giga Hertz or higher are called Hypersonic Waves. The term Acoustic Wave is a more general term to refer sound or vibration of any frequency. In physics, Acoustic is the branch of science which deals with the study of any mechanical wave in the solid, liquid and gaseous medium. Acoustic Waves are longitudinal waves.
Audio is one of the most common media. Here, It refers to the representation of sound which can be perceived by humans. Audio and Video are the essential component of any electronic media. The electronics can be used to receive audio signals (via microphone), record audio in some storage, transmit audio (through wired or wireless communication channels) and reproduce audio signals (via speakers). The audio can be represented and transmitted as either analog signals or digital signals. In this series, analog audio signals are the concern. The audio signals have a frequency range of 20 Hz to 20,000 Hz.
Lithium-ion batteries are another popular type of batteries that are used in the Uninterruptible Power Supply (UPS) designs. These batteries are commonly used in portable electronic devices. These are low maintenance batteries having high energy density, small size and light weight which makes them suitable for use in most of the portable devices. But, due to high energy density in comparison to the weight and volume of the Li-ion Battery, there are also some safety concerns while charging the Li-ion batteries. Before designing a charger circuit for these batteries, let us first understand charging methods and topologies involved in charging Li-ion batteries. Also, precautions required in handling, storing and disposing of these batteries are must to know.
The Uninterruptible Power Supply (UPS) is an electronics device which supplies power to a load when main supplies or input power source fails. It not only acts as an emergency power source for the appliances, it serves to resolve common power problems too. Any UPS has a power storage element which stores energy in the form of chemical energy like the energy is stored in batteries.It is like energy is stored in the form of motion in a flywheel. That is why these devices are also called battery backup or flywheel backup. The UPS not only provides emergency power, they also help to sort out common power related issues like providing protection from input power interruptions, protection from overvoltage, output voltage regulation and stabilization.
LM317 is commonly used for voltage regulation in DC circuits. The IC is one of the popular adjustable positive voltage regulators that comes with features like over voltage protection, internal current limiting, overload protection, low quiescent current (for more stable output) and safe area compensation (its internal circuitry limit the maximum power dissipation so it does not self-destruct). Apart from many features, less number of components are required to make it operational. So, LM317 regulator is easy to use and assemble in a circuit. In this project, an adjustable power supply using LM317 is designed which inputs main AC supplies (220V-230V AC) and outputs DC voltage below 12V. The LM317 has an adjustable output voltage of 1.28 V to 11 V and draws maximum 1.5 A current.
In the previous tutorial, an audio crossover was designed using high pass and low pass audio filter. In this tutorial, an audio equalizer will be designed. An Equalizer (abbreviated as EQ) is an audio equipment which cut or boosts the certain frequency components from the audio signal. This process of adjusting the frequency components is called as Equalization.The equalizers are widely used in the audio systems during recording of sound as well as in amplifiers and mixers. As they are used in the audio system so are called Audio Equalizer.
In the previous tutorial, an audio equalizer was designed. In this tutorial, now an audio mixer will be designed. The Audio Mixer is an electronic device which combines and modifies the audio signals. The audio signals can be either in digital form or analog form. In digital form, the analog audio signals are encoded so that the audio information in the signal becomes independent of the amplitude of the signal. Both analog and digital signals can be combined by different types of audio mixers. For mixing digital audio signals, digital signal processing techniques are used while for combining the analog audio signals, generally operational amplifiers are used.
In the previous tutorial, fundamentals of audio filters were discussed. The audio filters can be passive or active depending upon the use of passive or active components in their designing. On the basis of frequency response, filters can be classified as high pass, low pass, band pass, Notch, band reject, T-Notch, all pass and equalizer filters. In this tutorial, an audio crossover will be designed. The Audio crossover is an electronics circuit which splits the audio signal into two or more frequency bands. These frequency bands are then, sent to the different audio drivers (Twitters, Mid Range and Woofers). A single speaker is not capable to serve the whole range of audible frequencies due to the limitations of its construction. So, different drivers (speakers) are required to deliver different range of audio frequencies.
In all the previous tutorial, a pre amplifier using MAX4468 was designed. On the basis of application, there are two types of audio amplifiers – 1) Pre-Amplifier2) Power Amplifier The pre-amplifiers are used to level up the audio signals from a microphone or audio source to standard voltage levels while the power amplifiers are generally used at the output stage of the audio systems to boost audio signals before they are reproduced by the speakers. As the name suggests, a Pre- amplifier prepares the signal which is coming from the microphone or line input for further processing and transmission of the signal. A preamp is the hidden part of any device. It is integrated in the USB microphones, sound cards and mixers.
In all the previous tutorials, power amplifiers were designed. On the basis of application, there are two types of audio amplifiers – 1) Pre-Amplifier2) Power Amplifier The pre-amplifiers are used to level up the audio signals from a microphone or audio source to standard voltage levels while the power amplifiers are generally used at the output stage of the audio systems to boost audio signals before they are reproduced by the speakers. As the name suggests, a Pre- amplifier prepares the signal which is coming from the microphone or line input for further processing and transmission of the signal. A preamp is the hidden part of any device. It is integrated in the USB microphones, sound cards and mixers.
In the previous tutorials, the amplifier circuits to boost audio from a single channel were designed. Over the last decade, there is growth in the audiophile. This has brought a revolution in the music industry. Now, people like to hear the high resolution surround music just like a 3D video. A surround sound system is designed to create a sound field like the sound is coming from back, front, left and right sides. It can also create the sound above the listener. The surround sound system is used in cinemas and drama theaters to give a realistic feeling to the audience.
Continuing with the designing of application specific power amplifiers, in this tutorial a low power amplifier will be designed for regular mobile headphones. In the previous tutorial, a car audio amplifier using TDA2003 IC was designed. The mobile headphones are a type of miniature speakers designed especially for use with smart phones. These headphones do not have louder sound output. However, their sound quality can be improved by using an amplifier circuit with them. For headphones, a low power amplifier need to be designed.
When using MOSFET as a switch, it can be connected in two switching modes – high side switch and low side switch. Contrary to low side, the high side configuration of MOSFET requires some external circuitry to turn it ON. There are various methods for driving the high side MOSFET. The following three methods are most commonly used to drive a MOSFET as high side switch – 1. Dual power supply method2. Gate Driver IC method 3. Bootstrap circuitry method
MOSFET are more commonly used transistors. They are known for their high switching speed and high input impedance. That is why they are preferred to be used in the fabrication of integrated circuits and the high frequency application chips. Individual MOSFET are also widely used in lots of applications. Before using a MOSFET in a circuit, it is important to check if it is not faulty. In a defective MOSFET, the drain may get shorted to the gate. This can cause the drain voltage feedback to the gate terminal and this voltage then feed to the driver circuit through the gate resistor which can blow the driver circuit further. Therefore it is better to test the MOSFET before using it in the circuit. As N-channel MOSFET are more common so testing of N-channel MOSFET is only discussed in this tutorial.
In the previous tutorial, a Bass Boost Power Amplifier was designed. Now it’s time to start designing power amplifiers suitable for specific applications. In this tutorial, a car audio amplifier will be designed. The cars have been coming with inbuilt audio systems from years. An audio system of a car is one of the important features that shines as unique selling point (USP) for any car in the market. The audio systems have become a vital accessory for any car. Even many times consumers replace the default audio systems came in their car with new one for better driving experience.
While designing the UPS circuits, MOSFET were used in the inverter circuits. The MOSFET were used as High side switches in the circuit. For driving the MOSFET in high side configuration, IR2110 gate driver IC was used. IR2110 is a High –Low side Gate Driver IC which is used with power MOSFET and IGBT. A Gate Driver is a specially designed circuit that is used to drive the Gate of MOSFET or IGBT in High Side Switching application. That means when MOSFET/IGBT is used in High side configuration then a Gatedriver IC is need to be used. In this tutorial, some important concepts like the High and Low side Switching of MOSFET, need of Gate Driver circuit and driving methods of High side MOSFETs will be discussed. These concepts will crystal clear the working of MOSFET as a switch and will so justify the use of MOSFET in inverter circuit as switching component.