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The audio amplifier is a type of circuit used for amplification purposes. The audio signal is given to the input of an amplifier through a microphone or some other device which will be amplified through the circuit and get at the output through a speaker, etc. At the start of 1900 vacuum tubes were used for the sound amplification process after that in the 1970s these vacuum tubes were replaced with bipolar junction transistors and MOSFET. The most commonly used amplifiers are Class D amplifier that is constructed through the use of transistors and MOSFET since they have less weight structure and low heat dissipation.

Create an Audio Amplification Circuit

Audio Amplifier circuit

The components needed to create the audio amplifier are listed below, please purchase circuit board components before starting the project:

  • トランジスター
  • Speaker
  • Resistors
  • NE555
  • Power supply
  • Audio Signal

In this circuitry, there are transistors NPN configured is used. Transistors are electronic component that has two N and one P region for NPN configuration and two P and one N for PNP configuration. It has three terminals emitter, base, and collector. NPN configured transistor used that has given the input signal and output of that signal will be gained at the speaker. Some factors must be noted during the construction of audio amplifier circuits like frequency response, noise, gain value, and distortion. If the value of gain is high and distortion and noise are high then negative feedback will decrease the gain of the amplifier.

The working operation of the amplifier consists of more than one phase. Amplification is performed in numerous phases. Signal amplification is based on hall impedance value and infrastructures. The use of output signal defined its application value means for which projects what level of amplification is needed. The input signal is produced through the use of mike and that goes to the base of transistors. As transistors have two charge carriers that are majority and minority on basis of transistors. So after getting the signal from the input they start the motion, in the case of NPN transistor depletion region is less so charges cross the barrier, and current flow through the transistors or mean it starts operation.

In this circuit signal from the transistor is given to the NE555 pinout five. On the basis of signal demands numbers of transistors can be varied in circuitry. Since transistors use help amplify the signal to the required value. The amplified signal is known as the amplification process.

In the circuit, 9 volts power supply is given to pin 4 of the timer. Output or amplified signal is given taken out from pin 3 and given to the speaker where we can listen to the amplified signal that provides at the input.

Types of Audio Amplifiers

Class A Amplifier

Class A amplifier is easy to construct and simply configured more than other types of an audio amplifiers. Its operation is that all output devices connected to it operated through a complete three-sixty degrees signal. It can be configured into one-ended and thus, pull configurations. The push/pull structure uses the output devices in groups. These devices are operated through the complete signal cycle, one device is operating at the positive half of the signal and the other at the negative half of the signal. This configuration helps to decrease the distortion of the signal. With that push-pull class, a structure needs less conditions to operate while signal ended circuit needs more attention to operate

Class B Audio Amplifier

As above, FSテクノロジー discuss that for complete signal all devices of class A are operating but for Class B amplifier half devices operate for push/pull configuration. Such as for positive half of signal half devices operating and other half are not operating. So class B amplifier is more effective than the Class A amplifier, therefore it is used in different projects. Either they have high efficiency but are not commonly used due to crossover distortion

Class A/B Amplifier

Class A/B amplifier is created through the use of class A and Class B amplifiers to get the same advantages for one circuitry. This amplifier configuration is very commonly valuable in the electronic industry. The operation of this amplifier is that for half cycle class B operates on a push/pull structure, so the A/B amplifier amplifies the signal up to 181 to 200 degrees. This phenomenon helps to reduce the crossover distortion existing in class B

Class G & H

To enhance efficiency, and good operation there is a type of audio amplifier is created that is class G and H. It is construed by making some changes to the class A/B structure that uses voltage rail switches and rail modulation. For low demand structure system uses low rail voltage and then a class A/B amplifier that decreases the power consumption, when high power condition needs the circuitry increases the rail voltage to maintain high amplitude transients

As rail switches use BJT transistors for control of output rails which increases the circuit cost of construction. Nowadays there’s MOSFET used in place of BJT for rail creation. The use of MOSFET increases the efficiency of the circuit which reduces heat dissipation. With a reduction in the cost of construction, these amplifiers can handle more output devices than Class A/B amplifier. Its structure is such that one pair of devices operate in an A/B configuration that gets the low voltage and the other pair operates as a voltage booster.

Class D Amplifiers

These amplifiers is known as digital amplification which denotes an increase in the amplifier efficiency since it provides about ninety percent efficiency. Its operating speed is high so it switched the output devices into on and off states very fastly. It switching rate s about 50 megahertz. Output devices are controlled through us pulse width modulation, the square signal is produced through a modulator that helps to reproduce of the analog signal. Through control of output devices provides about one hundred percent efficiency.

These amplifiers are most efficient than other types of amplifiers and have low weight structures that helps to be easy to construct and easy to use

Audio Amplifier Applications

The simple power amplifier has such a circuit configuration that gets low strength audio signal and produces a signal that has high strength. This technique is used in numerous projects where the electric signal is transformed into a sound signal. This amplifier is called an audio amplifier. Any category of a circuit that performed the processing of audio signals at input and output consists of the audio amplifier circuit. A common example of an audio amplifier is a Bluetooth PCB that gets the audio signal that the amplified to a high level and we hear amplified sound at the speaker or transmitter. Some applications of amplifiers are discussed here:

  • transmission of wireless signal audio amplifiers is used
  • To transmit the signal to long distances these amplifiers are used.
  • The radio stations used this amplifier for signal transmission
  • It used in different electronic projects and devices
  • Amplifiers need has become very common for any DIY PCBA projects and circuits to amplify the signal to the required level.

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