Audio Amplifier Circuit Using Mosfet Transistor

Introduction: Audio Amplifier Circuit Using Mosfet Transistor

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How to make an audio amplifier using just one mosfet transistor

An audio power amplifier (or power amp) is an electronic amplifier that strengthens low-power, inaudible electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is strong enough for driving (or powering) loudspeakers or headphones. This includes both amplifiers used in home audio systems and musical instrument amplifiers like guitar amplifiers.There are lots of circuit diagrams out there but we have selected the easiest one that has a mosfet transistor.

Step 1: Simple Power Amplifier Circuit

Simple power amplifier circuit components

Power amplifiers make the signal—whether it is recorded music, a live speech, live singing, an electric guitar or the mixed audio of an entire band through a sound reinforcement system—audible to listeners. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers and speaker enclosures.

Poweramp components :

Mosfet transistor IRFZ44N

Resistor 10K

Capacitor 440v 30mF(not crucial)

Speaker+Jack cable+power supply(5v-9v)

Step 2: Jack Audio in Cable Connection

In order to make the audio input for our audio amplifier we have to make the connection from the audio into our amplifier, for this, we will need a jack mono/stereo cable.How to find the correct cable connection is very simple

this type of cables from bottom to top have layers divided by some small black strips.Now on the bottom part and also the bigger part is the ground or negative terminal, and the rest is positive or signal left and right if is a stereo cable.For this you will use the multimeter in the continuity selection and from each metal connection of the jack audio cable to the opened wires wi will find which one is which.

Step 3: Audio Amplifier Circuit Using Mosfet Transistor

You have the circuit diagram of a simple audio amplifier using a mosfet transistor and the representation of each electronic components and the connection between audio in and speaker audio out.

While power amplifiers are available in standalone units, typically aimed at the hi-fi audiophile market (a niche market) of audio enthusiasts and sound reinforcement system professionals, most consumer electronics sound products, such as clock radios, boom boxes and televisions have relatively small power amplifiers that are integrated inside the chassis of the main product.

Step 4: Audio Amplifier Sound Test

Let's make a sound test in the video linked you will find the sound test of our homemade audio amplifier with simple electronic components, now this is not going to replace your home system or subwoofer this is just the practical application and demonstration of an audio amplifier in its primitive form.

The audio amplifier was invented in 1909 by Lee De Forest when he invented the triode vacuum tube (or "valve" in British English). The triode
was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the first AM radio. Early audio power amplifiers were based on vacuum tubes and some of these achieved notably high audio quality.

Thanks all for participating and please check the video for more details and practical representation of this primitive Audio Amplifier circuit i hope you will see the practical and simplicity of the project and not so the errors if you want more electronic projects visit NoSkillsrequired youtube channel.



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    9 Discussions

    I have a Rockford fish are T2500 1bd amp an i blow a few transistors how do i find out wat size they are an where can I buy new ones

    This is a Class A power amplifier topology that was common in electronics hobby magazines and kits from the 1950s when power transistors were expensive. The circuit is very simple and it does work, but those advantages are achieved at great cost to efficiency.

    The major drawback with this design is the IRFZ44N. That transistor is optimized for switching applications and isn't really suitable as an amplifier. It is quite non-linear between non-conducting and saturation states and can have a gate threshold voltage anywhere between 2V and 4V depending on the manufacturing batch. This makes it hard to predict where the center of the load line will end up and causes a great deal of distortion in the output which goes uncorrected without a feedback network.

    If you happen to get lucky (or unlucky depending on your point of view) and the IRFZ44N you get has a threshold voltage sufficient to place the output at 1/2 power supply voltage, the dissipation in the speaker will be 2.5W, and dissipation in the IRFZ44N will also be 2.5W. All that heat and no sound. As you can see in the video, the speaker cone will also be advanced from its neutral position which leaves less room for the cone to travel before over excursion. Output current will be 562mA, which gives an Alkaline battery about 12 minutes of run-time accounting for ESR and a collapsing load line. And finally, the IRFZ44N will become quite warm in operation requiring a heat sink.

    A bipolar power transistor or an FET suitable for linear applications would work much better. But a 9V battery would still have a very short run time.

    The 450V 30uF electrolytic is massive over specification. I have no explanation for why this was specified. A 25V electrolytic is fine and costs only $0.10 instead of $1.15.

    In my testing the amplifier does work if you sort through a few IRFZ44N transistors and pick the one with the greatest output swing. Good for a quick demonstration and fun to see what can be accomplished with just a few parts. But it's not a practical amplifier for every day use.


    Should the capacitor not be in series with the output, rather than the input? To prevent DC bias from driving the speaker?

    1 reply

    The gate to drain is isolated from source to drain

    The voltage determines the conductivity of the mosfet. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals.


    8 months ago

    This is no good design, since there is always a high dc current flowin through the speaker which will drain the battery rapidly and also is not good for the speaker.

    1 reply

    This is the simplest audio amplifier ever and current can be restricted,and with a 9v battery it draws 0.07A


    8 months ago

    Just to clarify what an amplifier actually does. First it doesn't MAKE anything. If that were true, we would have no energy issues ever. It merely allows you to control the supply power with a little signal at the input. In other words, you can control a large amount of available power with a little amount of signal. You can't make more output then the available power input. Once that is understood, amplifiers can be understood much easier. JMHO

    1 reply

    This is what i said in the first line of this AUDIO amplifier instructable its nothing related to the free energy concept, that's another topic my friend all the best

    How to make a simple audio amplifier circuit