Low power Transistor or MOSFET ??

Gayan Soyza said:

I need to replace standard NPN transistors (with additional base resisters) with a single MOSFET to work with 2.4V-4.8V (batteries).

I'm planing to place 2N7000.Data sheet says its designed for low power applications but looks likes it needs 2.1V Ggs.

Anybody have worked with this MOSFET with low voltage range like 2.4V-4.8V??

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Gayan Soyza said:

Hi Eric Thanks for your input.

I need to light up my 5X7 LED small matrix system.

In that matrix one LED takes 22mA current.I need to drive one column of LEDs (7 LEDs) with this 2N7000.So for 5 columns I need 5 MOSFETS.

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Gayan Soyza said:

Hi Eric thats a nice graph thanks.

The thing is my project is battery operated.From the graph below 3.5V is not going to provide sufficient current.

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ericgibbs said:

hi,
Whats the driving source for the 2N7000 gates are you using a PIC or some other ic.?
Whats the project.?

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Gayan Soyza said:

Its a mini 5X7 LED matrix project.I'm using a PIC.

Most important thing is this must power from batteries.

This is a hand held project so it must use batteries.To make the design compact I planned to use MOSFETS instead of BJTs.So I can eliminate base resisters as well.

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ericgibbs said:

hi,
Have a look at this dual.

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Ubergeek63 said:

Oh yuch! 0.5mm pitch and little stubs instead of leads.

https://www.electro-tech-online.com/custompdfs/2008/12/FDC6401N-1.pdf

<0.1Ω @ 2.5Vgs @ 2.5A in a SOT23 and available in singles for $0.50 from digikey.

Dan

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Its a mini 5X7 LED matrix project

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Gayan Soyza said:

I planned to use MOSFETS instead of BJTs.So I can eliminate base resisters as well.

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ericgibbs said:

Retails in the UK at £0.2, not bad for a dual, decent spec.

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Ubergeek63 said:

Well I have to admit that I neglected to check what price I was up against... I was more up at arms over the package really.

It is not easy to solder that pitch by hand when there are leads, never mind when there aren't. I am assuming he is trying to solder leads to it, as most here would not have PCBs for that kind of work.

Dan

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ericgibbs said:

hi,
I bought some ADS1100 16 bit adc's recently, they are small!, I have a bench magnifier and they are still small.
The solder iron tip looks like a jack hammer.

The idea is to mount one piggy back on a 16F876, using Kynar to wire the legs to the SPI lines of the PIC, pick up the PIC power and 'share' an analog input.
Its going to be a rainy day job..

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