MOSFET or other component to control power?

I’m tinkering around with an audio project consisting of an Arduino Pro Mini (5v version), a DFPlayer MP3 Module, a TDA2822M Amplifier Module, and some 8 ohm 1 watt speakers.

The amplifier module requires 4.5-9 volts DC. I’m thinking of using a 9v battery to give the audio a boost. To prevent battery drainage when no audio is playing, I would like to power the amplifier only when audio is playing; the audio will play infrequently. Originally, I was considering a solid state relay module to avoid introducing noise into the circuit, but the options I have found so far are designed for AC loads.

Can I use a MOSFET to reliably control 9v power to the amplifier?

From what I have read so far, it appears that a MOSFET doesn’t latch. Can one combine a MOSFET with another component to create a latching circuit?

Or, is there a different component more suited to this task that would work similarly to a latching relay?

Can You specify that? I have suspicions......

USe an amplifier that doesnt draw significant current when its not producing an audio output - a class c or d

Hi Railroader! :slight_smile:

I would prefer to use the 9v battery rather than the 5v transformer powering the Arduino as it should improve the audio volume.

Specify that battery! You might be on a totally wrong path.

I was thinking a 9v alkaline battery

I cry. That battery is a voltage cell, not a power cell, not a nuclear power station. It's not useful for any serious project. It might make simple things start up but all will black out in minutes.
Started playing with batteries and bulbs being 5 years old and soon learned the difference between batteries. I'm 68 years old now...

On the other hand, that battery in its zinc carbon infancy was known as a “ transistor radio battery” and did offer some operating time with acceptable cost.

If the OP is only running a small audio amplifier section of his project with this battery, esp. in its modern alkaline old age, s/he might not be tots disappointed.

Combined with using as @Railroader suggests an amplifier of low power when no signal class, it might be more than equally acceptable.

I agree that to power the Arduino, given the linear voltage regulator it uses for 5 volts, is a no starter.


@ alto777

You are right but there are lots of ifs and restrictions that I don't feel OP is aware of.

This gives me bad vibrations.

1 Like

Thanks everyone for the input. I should have specifically mentioned that the Arduino and the DFPlayer will be powered by a 5 volt transformer. Only the amplifier will be using the 9v battery to boost the audio volume. The MOSFET would be used to control when the amplifier could draw current from the battery and would also ensure that the 5v to the Arduino and 9v to the amplifier remained separate.

As the audio to be played is only 10-15 seconds, and will only be played once or twice a day, I would expect the 9 volt battery to reasonably last about a month or two.

Markus Wobisch has published an excellent article on using the DFPlayer including many improvements that result in very clean audio. I have built a similar circuit following the advice he provides. However, as I am still waiting for the amplifier to arrive, I have simply connected the speakers to SPK_1 and SPK_2. The sound is good, but quiet.

From what I have read so far, it appears that a MOSFET doesn’t latch. This would suggest that an Arduino pin would have to be made high and kept high to keep the 9v current running to the amplifier. Which makes me wonder if a MOSFET is the way to go, and whether one could combine a MOSFET with another component to create a latching circuit?

Yes, that is the way to go. Think about it: you need an output pin to run it, so the “latching” you speak of is just done in software, keep the pin in the state that drives the mosfet.

So even if it was a external latch of some design, you still need an output pin…



Thanks for the input alto777. It seems that a MOSFET is on the right track!

After hours of reading on this topic, I have come across a really good MOSFET article here. Perhaps this will be of use to others who might come across this post.

Sometimes you gotta kiss a bunch of frogs before you find a prince.

That’s a nice article, I almost wish I needed to read it carefully.

It has been recommended that one should keep looking - give every resource a fair chance, but move on if it is too simple, too hard, too boring or you just don’t like the guy or the chick or you prefer reading to watching or or or.

What a great time to be alive, I cannot imagine how we ever got anywhere in the old daze.


Realize that your amplifier will be dead for up to a second after power on because the capacitors need to be charged. You don't notice it now, but will if you continue with that method of controlling it's power.

No kidding!

Thanks, Paul for mentioning this! I will code a short delay before the audio is actually played.

Sadly, when you do you may find it wanting. Can't speak for the video as YouTube routinely crashes this PC.

Fails to explain the need for saturation on BJTs and the significance of logic-level FETS. Fails to explain the limitations of Darlingtons.

So people are likely to come here (hopefully for them) when things go pear-shaped. :worried:

I won't harp on the smoke alarm batteries. :grin:

I think 9V might be too much for the speakers. I will try with everything powered via 5V, and if it is satisfactory, leave it at 5V.

By comparison, the voltage from a typical audio jack is approximately 1V.

I tried a simple analog amplifier with a .. TIP32CFS (datasheet) and a audio jack with 5V over USB. It was sufficiently loud that the speaker (the same 8Ohm 1W) are "booming".
For reference, the parts come from ADALP2000.

I don't think you need a TDA-2822M. go find a PNP (or NPN) and wire everything up with 5V. Then toss in a adjustable resistor to the amplifier gate and see if you are pleased with the result.
Amplifier class D PAM8403.
Supply Voltage from 2.5 to 5.5 V.
Output Power THD+N = 10%, f = 1KHz, RL = 8Ω VDD = 5.0V 1.8W.
Efficiency RL = 8Ω, THD = 10% f = 1kHz 87 %.
Shutdown Current < 1 µA (has shutdown pin, not needed MOSFET or relay).
Price < US $1.50 with free shipping for 5 pcs from AliExpress.

Thanks for taking time I was too lazy to didn't.

At a glance it seemed to cover a good number of the basic issues, &c. Too bad it doesn't measure up; it seems that the general scope and tone could be maintained without glossing over things, dumbing them down or making outright mistakes.

My experience of contacting authors of all kinds with "suggestions" has left me not doing. Even when dangerous obvious demonstrable errors exist, ppl tend to get defensive fast. Not to say that would be the case in here, but Imma leave it alone.

Which points up the utility of having multiple channels of learning open. When there is disagreement it can guide further researches. And there is nothing like a good protracted thread on these fora where we get some real time discussion. Other sites are good for that, too.

What we do here is at least based in reality, so there are facts and the empirical process.

With other fields, one is more likely to fall victim to confirmation bias, as just about any opinion can be found to have support on some corner of the internets.


Yes - can't say from experience I am terribly enthusiastic either about getting people to "improve" their blog details, especially when it means re-drawing a schematic. :face_with_raised_eyebrow:

(You probably know my favourite "hobby horses". :grin: )