Transistor Substitution Chart

[Dragonfly]

Nothing that the "vets" here don't already know...but I made this little chart up for some of the "newer" guys. If a schematic calls for a transistor that you don't have, this chart should give you some other options...at least for some of the more "common" transistors. Also, if the transistor you need isn't listed, you can look up the datasheet ( www.datasheet.com ) and find out if its silicon or germanium, PNP or NPN, and this chart will help you find some options. I'll probably make up a far more "extensive" chart in the future, but this will be a "start"...

Also, it's posted in my Layout Gallery...

AC

[searoad]

nice!
very helpful!!

[Roobin]

That's amazing! Just what we needed!

LOL "even ebay"!

[R.G.]

Good for the beginners.

A couple of points that might help.

The J201 has the lowest Vgsoff I've seen. MPF102 and 2N5457 are not really good subs for it. Better subs are 2N5485, 2N5292, 2SK30A and 2SK117.

There is no point in listing "NKT275" for anything. There aren't any. I've looked for years and so have other people as close or closer to the germanium biz than me.

For germanium devices, the listed subs are generally not available on the web at all except at places that find and preselect them. It would be better to tell the newbies to go to Small Bear than to tell them to look on the web for germanium or at the big distros. It's probably better to warn newbies that ebay is a great place to buy batches of germanium devices that are the remaining scrap from unscrupulous pre-testers reselling their leftovers.

It would be a help to add Euro (BC...) and Japanese (2S....) equivalents to the silicon devices section. And to add "germanium diode types" of 1N34, 1N34A, 1N260, etc. to the chart, also adding the note that the leftover scrap germanium transistors on ebay are useful for germanium diodes if you cut off the emitter lead and the cost is low enough.

I guess it would be more helpful for me to write some more of this up.

[Ronsonic]

I guess it would be more helpful for me to write some more of this up.

I think you just did.   

Ron

[Hiwatt25]

Does such a list for exist for IC substitutions?  Some of the IC's I see listed for popular projects seem obsolete or very hard to find. 

[Willy]

Great! It would be fine if the pinouts can be included.

[Dai H.]

speaking of subs, here's a site I stumbled on recently which has some cross ref info and simple data for some obsolete Japanese transistors like 2SB prefix PNP Ges.

http://www5f.biglobe.ne.jp/~soichiro/elec.htm

[choklitlove]

somebody should wiki this.  nice dragonfly!

[Gus]

The Jfet part

Jfet subing takes some effort.  A "good" sub is the same die in a different package metal, plastic, pinout, spec sort.

A j201 is best subbed with a j201 

But then again using trim pots in the drain leg does not make sense to me
the drain current is changing so the posssble output drive current is changing
but if you adjust the source resistor the input head room changes but the Id can stay the same so it is all a compromise or or you select the parts before the build..................................................

  There are some good sites with information about fets on the web.

Fets are good for one at a time but when you try to build a few you need to test them for IDSS and  ..........

[Jay Doyle]

But then again using trim pots in the drain leg does not make sense to me
the drain current is changing so the posssble output drive current is changing
but if you adjust the source resistor the input head room changes but the Id can stay the same so it is all a compromise or or you select the parts before the build..................................................

This is why I advocate biasing at the gate with a trim as a voltage divider instead of the drain as a variable resistor.

[aron]

The interesting thing is that for the J201 transistors I sell, I have had extremely good luck simply putting in a 15K resistor for the drain, 1M for gate and I believe 1K for the source. Biases right up at right around 1/2V+. I haven't been using trims for a while with these transistors. They seem to be pretty darn good at biasing right up.

[Dragonfly]

these are all good points...and obviously it'd be cool to eventualy make up a chart that includes all of these things and more...but this was just meant to be a "beginners guide"...

the reason i mentioned the NKT275 has nothing to do with "you can find them"...it has to do with "the schematic calls for a NKT275, and i can't find one...so anything else on the same "line" of (more or less) eqivalents should work.

I thought about the diodes thing, but i dont see nearly as many "beginner based" projects with germanium diodes....and the projects that "do" have germ diodes usually specify 1N34A, which are readily available..

[WelshWonder]

Am I being blind or is his chart no longer available?

[Dragonfly]

it's in my layout gallery.