Understanding Mosfets

[abishur]

I've been trying to learn about Mosfets and feel like I'm missing something important.  By all respects they seem like a way to control higher voltages using the Arduino without having to worry about current draw form the arduino like you would when using a transistor.

But whenever I look at enhancement N Mosfets that come in multiple channels I almost only find common drains.  What is the point of this???  Drain is what I connect my load up to, so why would I want to be able to a single load using two different gates on the Arduino?

Am I just misunderstanding how an N type mosfet is wired?  Source goes to ground, Drain goes to load, and Gate goes to my Arduino, right?

I know I'm missing something, but I feel like I'm going crazy as I can't figure out what the benefit is from being able to turn a load on using two different pins on the Arduino.

[saildude]

Does this help?

https://create.arduino.cc/projecthub/ejshea/connecting-an-n-channel-mosfet-7e0242

[abishur]

Thanks for the response, but no it doesn't help I understand the basics of how to wire it and make use of it, my hold up is understanding why when it comes to multi-channel N mosfets why is that by far and large they tie the drains together?

I can find some multile N channel mosfets that have nothing tied together, it's rare but I can find N channel mosfets that tie source together (which makes sense if I'm using it as a switch), but why is it that most of them tie the drains together?

I'm thinking if I understood that, I would have a better knowledge of what mosfets are really useful for.

[JCA34F]

Which MOSFET? There are hundreds. Post a part number.

[hammy]

Some are used in precision bridge rectifiers and that could be a reason .

( you dont get diode voltage drops)

Try looking for " FET array" it might be more successful ? They are out there , I just found a couple with all pins bought out

[Paul__B]

Sorry, but until you cite (Web link) the actual datasheet for one of these curious FETs to which you refer, this is all nonsense!  

[JCA34F]

Are you confusing multiple drain connections with the common drain (source follower) amplifier configuration?

[abishur]

Which MOSFET? There are hundreds. Post a part number.

Well I was asking about any given multichannel N Mosfet where the drains were tied together as that seemed to be the type I was encountering the most (ergo it stood to reason that this was the most commonly used type and there had to be a reason for that)... but to pick one at random, https://www.diodes.com/assets/Datasheets/ds31995.pdf

Now it might just be that as I was looking around I happened to hit only references to common drain type mosfets causing my beliefs to be skewed.  BUT, if common drain types are the most, well, common there's a reason and I'm trying to understand that reason so I can better understanding mosfets.

[abishur]

Are you confusing multiple drain connections with the common drain (source follower) amplifier configuration?

based off the included picture, I do not believe so.  The ones I saw were all 2 gates, 2 sources, and a common drain between them.  From my basic level searching I had come to believe this was common (as it seemed any time I did a search for (2 channel or dual channel N mosfet) the common drain was the one everyone was talking about.  However, based on the responses here I'm starting to doubt that belief, lol.

[CrossRoads]

That was the first time I had seen a configuration like that.  I cannot think of a design that would take advantage of that.
I could see connecting the gates and sources together and just using it as a low Rds, Logic Level,  SMD N-channel MOSFET.

[JCA34F]

I think you want a transistor ARRAY:
https://www.mouser.com/new/toshiba-semiconductors/toshiba-tbd62064a-array/
https://www.mouser.com/ds/2/408/TBD62064AFG_datasheet_en_20151217-938289.pdf