Go Down

Topic: Amplifying current with high power transistor (Read 1 time) previous topic - next topic

6v6gt

Would the RFP30N06LE be an alright option?
That looks OK. I see, however, that Mouser list these as obsolete. In that case, IRLZ34PBF  may be a better choice.
It is actually overkill for your application but your choice of logic level power mosfets is limited unless you can work with SMD components.

Rapid80

So I can't get the IRLZ34PBF cheap and fast on amazon, so I will go with the rfp30n06le. Do you think I would need a heatsink? I already have a small one.

PaulRB

#17
Mar 26, 2020, 08:00 pm Last Edit: Mar 26, 2020, 08:14 pm by PaulRB
Do you think I would need a heatsink?
For 1.5A? No.

But check it after a few minutes, and after an hour. If it burns your finger, you need a heatsink. But I don't think you will need one.

MarkT

If it burns your finger, you need a heatsink. But I don't think you will need one.
Also, if it starts to burn, let go!!
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Rapid80

#19
Mar 26, 2020, 10:00 pm Last Edit: Mar 26, 2020, 10:29 pm by Rapid80
Ok, so everyone is good with this decision? Just need to make sure I dont order the wrong one again. Thanks so much!

EDIT: Also, does anyone know what the expected Power dissipation might be? Also, if this thing always outputs 30 amps, wouldn't that destroy my motor?

6v6gt

So I can't get the IRLZ34PBF cheap and fast on amazon, so I will go with the rfp30n06le. Do you think I would need a heatsink? I already have a small one.
No. If you drive the gate at 5volts or higher, it will dissipate a maximum of 225mW at 1.5 Amps which you mentioned previously.

Rapid80

Oh, ok thats good to know. I am also confused on the wiring a little bit. For NPN transistors, the collector is where my output is, but collectors are like the source, base is like the gate, and emitter is like the drain, so how does that work? I am pretty sure drain is the output, but the drain is like the emitter, not the collector. How would I wire the rfp30n06le in place of "Q4" on my circuit? Thanks for the clarification.

MarkT

No, emitter is like the source, collector is like the drain.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Rapid80

Wait did I get that wrong? For NPN transistors, are collectors like the drain, base is the gate, and source is the emitter? If so that would make a lot more sense.

Rapid80

I was posting that when you did lol. That makes a lot more sense. I went back to the source where I found that comparison, and I saw that they were actually using a bc-557 to compare, and that is PNP, so I thought I may have gotten it wrong. Thanks so much! I can basically just pop the new mosfet in there and it should work! I am excited! Not sure if this was covered, but the motor wont get destroyed right? Do mosfets always output a current and that is all, or do they output what is being used? Not sure if that is the correct wording. Thanks again!

PaulRB

#25
Mar 26, 2020, 11:29 pm Last Edit: Mar 26, 2020, 11:36 pm by PaulRB
if this thing always outputs 30 amps, wouldn't that destroy my motor?
Do mosfets always output a current and that is all, or do they output what is being used?
The transistor is just a switch, it either allows the current, that would naturally flow, to flow, or blocks it. It cannot produce current out of nowhere, that would be breaking the laws of physics!

Rapid80

You, my extremely helpful friend, are right. I am so happy right now!!!!!! All my questions have been answered and I have no doubts about this! I cant wait! Thank you so much everyone! It would've really sucked if I had to find out the hard way that my transistor probably would've burned up. I already said this but I am so excited!!! Thank you all, and keep helping noobs like me. When the mosfets come in, I will let you all know how it goes.

PaulRB

#27
Mar 26, 2020, 11:55 pm Last Edit: Mar 27, 2020, 12:03 am by PaulRB
Its great to hear that you are happy and excited. But you are trying to run when you have not learned to crawl, let alone walk. You really must study and understand the absolute basic theory of electricity. Your questions have revealed that you don't understand the most basic concepts such as voltage and current, not even the conservation of energy. Without that you have no chance of understanding how circuits like the one you posted earlier, or the components in them, work.

Rapid80

Not going to disagree with you on that one. I am very new to electronics, and I just need to keep going on YouTube and watching videos on these things. I am notorious for getting into something or doing something or buying something before I actually know what I am doing, and I really need to work on it. I watch "Learnelectronics" a lot, and I have learned a lot from him. I appreciate you pointing out my weaknesses so that I can work on them.

Rapid80

Wait, one final question: in my schematic, I have a 1k resistor going into the base of "Q4". Can I still have a 1k going into the gate of the mosfet for current limiting, though it needs 5 volts?

Go Up