Transistor question

[K1LNX]

I am getting ready to build a small project that calls for 2N2222 NPN transistors in a TO-18 (metal can type) case.

I'm curious if there is any difference between a transistor in a TO-18 case versus a standard TO-92 (plastic) case? I think the most obvious difference to me is heat dissipation, but again I'm not sure.

Is there any other differences? Could I safely use a TO-92 casing instead?

tnx and 73's
Stephen
K1LNX

[KL7AJ]

Well, unless you're doing something quite unusual, you aren't going to be pushing the dissipation ratings of a small signal transistor like a '22. (I have seen a design for a linear amplifier that DOES use a whole truckload of those transistors, but I trust you aren't doing that). For most "normal" uses of the '22, any model is just fine. Supposedly the metal can is better shielded for VHF, but I've never seen any PRACTICAL difference at all.

eric

[AG3Y]

Like Eric says. Use what'cha got. Some years ago, boatloads of circuit designs were featured in QST and other publications using the 2n2222. I doubt, considering the frequency cutoff that they more than likely have, that they would ever go up to VHF frequencies. I suspect that the metal shielded the electronics more from ESD than anything else!

My take on it . 73, enjoy ! Jim

[K1LNX]

Sounds good guys and thanks for the insight! The TO-92 packages are cheaper anyhow, so I think I'm going to use them.

In case anyone is curious, the project I'm building is a programming circuit for a Yaesu FT-1802 2m rig.

You can read all about it here:

http://www.g4hfq.co.uk/download/g4tic.pdf

73's and tnx
Stephen
K1LNX

[KL7AJ]

Actually, the '22 has a gain bandwidth product of 300MHz! Although, I've never used them up there, either. There are much "gooder" vhf transistors.

eric

[K7JEM]

In fact, for that circuit, almost any type of small switching transistor would work fine. 2N3904, 2N2222, PN2222, or just about anything. There are no high voltages, or currents over a couple of milliamps, and the gain of the transistor shouldn't be an issue.

You can usually find these type of transistors for around 5 cents, if you buy in quantity, or around 25 cents if not.

Joe

[K1LNX]

Quote[/b] ]You can usually find these type of transistors for around 5 cents, if you buy in quantity, or around 25 cents if not.

Ordering parts from Mouser now, got 'em for .04 a piece, with no minimum!!! Can't beat it!

[AG3Y]

Quote[/b] (kl7aj @ June 20 2007,13:18)]Actually, the '22 has a gain bandwidth product of 300MHz! # Although, I've never used them up there, either. #There are much "gooder" vhf transistors.

eric

I didn't know that, Eric. #See, I DO learn something, every day !

Bet lead length would become a significant factor up there, though !

#73, Jim