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Topic: What transistor do I need? (Read 892 times) previous topic - next topic

V0R73X

Hi.
I have a 40mA current but I need it to be 700-1000mA. What transistor should I use?

retrolefty


Hi.
I have a 40mA current but I need it to be 700-1000mA. What transistor should I use?


NPN or PNP? Maximum voltage being switched?

V0R73X

NPN or PNP are both fine. The more popular the transistor is, the better, since I have a better chance for finding it in a store.
Maximum voltage should not go higher than 7V. The input voltage is 5 and it's fine if it stays the same, but a little bit higher doesn't kill either.

Techone

I will use two transistor, connect them in a Darlington configuration circuit. The transistor are 2N3904 ( max 200 mA ) and TIP31 ( max 2 A ) and don't forget a heatsink for the TIP31. and a base resistor for the first transistor and another one for the second transistor. Or buy a Darlington transistor Ic of 2 A or more.

CrossRoads

Are you sinking or sourcing current?
For those currents, I would suggest low Rds, Logic level MOSFETs.
P-channel for Sourcing current.
N-Channel for Sinking current.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

MarkT

My favorite choice (if you can find it) - ZTX851, NPN, high gain, high current (5A), low saturation voltage, in tiny e-line package...
[ I won't respond to messages, use the forum please ]

CrossRoads

Ugh, that part has awful #s:
IC=0.1A, IB=5mA*
IC=1A, IB=50mA*
IC=2A, IB=50mA*
IC=5A, IB=200mA*

Arduino only puts out 40mA, this part could only control ~0.7A.
And it costs $1.09.

This 48 cent MOSFET Logic Level (can control with 0/5V gate) can control all the current, and will run cooler.
http://search.digikey.com/us/en/products/NTD4960N-1G/NTD4960N-1GOS-ND/2409565
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Techone

@CrossRoads

I agree with you about ZTX851 about high IB needed to switch high IC. It need an another transistor in a Darlington config for this transistor to operated. I also notice the switching and bandwith is pretty good. Maybe that is why this transistor is expensive.

And I also agree with you for the OP to use a MOSFET Logic Level.

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