2n2222 Equivalent Transistor

[overtyle]

I'm building an interfacing relay for an RF receiver and it calls for a 2n2222 transistor. From what I've read, the 2n2222 is only rated at about 800mA max. Is there another transistor I can use in its place to run about 7A?

 

[MikeMl]

I would use a modern, logic-level gate NFET. Chances are, if the original circuit was only switching 500mA or less, the upstream driver probably cannot source the ~250mA of base current that a 7A NPN transistor would require. You could also look into an NPN Darlington, but they are harder to find, and cost more than a NFET.

What is the open-circuit output voltage from the device that drives the existing base?

 

[Ian Rogers]

To get 7A you'll need a darlington... I use the BDX33c to drive heavy currents, but I think you'll be hard pushed to get one as an "equivalent".... All the ones I can find are To220 packages...

 

[overtyle]

I don't know what the voltage is that's currently driving the base. I'm not the really electronics savy, but I'm learning. Below ill post schematics for the RF receiver and interfacing relay. I was told I could interface directly using a MOSFET.

 

[overtyle]

I know a MOSFET used little to no base current but needs more base voltage. I'm not sure if this circuit has enough output base voltage to interface with a MOSFET.

 

[MikeMl]

I know a MOSFET used little to no base current but needs more base voltage. I'm not sure if this circuit has enough output base voltage to interface with a MOSFET.

As long as you select an NFET with a Vt (threshold voltage) of less than 2V, the 3V decoder chip should drive it just fine. Digikey or Mouser sell lots of suitable devices.

 

[overtyle]

As long as you select an NFET with a Vt (threshold voltage) of less than 2V, the 3V decoder chip should drive it just fine. Digikey or Mouser sell lots of suitable devices.

I found a couple on mouser. There's the NTD4963N min. Threshold voltage of 1.45 maximum 2.5, NTMD5838 min. 1.0 maximum 3.0, and NTD6416AN min. 2.0 maximum 4.0. Which do you think would work the best?

 

[MikeMl]

Because the decoder chip puts out a max of 3V, I would pick the one with the lowest threshold...

 

[overtyle]

Ok so the NTD4963 would work the best with the 1.45v min. And 2.5v max.

 

[MikeMl]

Here is what **broken link removed** in through-hole parts sorted by increasing Vth