# Create a simple audio amplifier with a MOSFET

Hi, I am pretty new to Arduino and I have that little speaker from Sparkfun (https://www.sparkfun.com/products/10722). It's pretty loud, but I want to make it sound louder. I've read of many "simple" circuits, made with various transistors+resistors combinations, but I don't have (right now) some of the required materials, so I was wondering : can I make a sound amplifier with a MOSFET transistor like that one : MosfetTransistor.pdf (included in the Arduino starter pack)? I just need to amplify the square wave produced by the Arduino's tone() function.

You need 10 volts on the gate of that MOSFET to turn it on.
The Arduino outputs 5 volts.

Use a logic MOSFET ex: IRL540

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can I make a sound amplifier with a MOSFET transistor like that one : MosfetTransistor.pdf (included in the Arduino starter pack)?

No. Was it in the starter pack? It should not have been, it is not a logic level FET and so it will not turn on fully with 5V, it requires 10V. You will get something but it will get a lot hotter than it otherwise would and it will not be as loud as it could be.

Loose the 47R resistor to make it louder. Make sure your power supply can give the current required.

Loose the 47R resistor to make it louder.

I didn't want the OP to blow the Arduino up.

LarryD:
You need 10 volts on the gate of that MOSFET to turn it on.
The Arduino outputs 5 volts.

Use a logic MOSFET ex: IRL540

.

Thanks for the suggestion !
Just one thing : the 47R stands for a resistor of 47 ohms? Seems a little weird to me…

Yes

The R is used for ohms as there is no Ω symbol on the keyboard.

Standard electronics notation:

0R12 = 0.12 ohms (120 milliohms) 3R3 = 3.3 ohms 33R = 33 ohms 3k3 = 3.3k ohms 2M2 = 2.2M ohms

The letter stands in for the decimal point because a printed '.' on a component is very easy to miss (or be rubbed off / illegible).

Same goes for farads and henries, ie 2n7 on a cap is 2.7nF, 47m on an inductor would be 47m.

LarryD: The R is used for ohms as there is no Ω symbol on the keyboard.

Heh, heh. ½µ°

Paul__B: Heh, heh. ½µ°

+1 You passed the test ;) .