there's got to be a better way!

[terryrocks]

the circuit I'm trying to build requires two 2n3904 with HFE close to 200.

I ordered 20 of the damn things and all of their hfe's are right around 110 with very little variation.

How am I to get the correct transistor hfe?  previous advise was to buy a bunch and that's not working out for me.

[tiges_ tendres]

the circuit I'm trying to build requires two 2n3904 with HFE close to 200.

I ordered 20 of the damn things and all of their hfe's are right around 110 with very little variation.

How am I to get the correct transistor hfe?  previous advise was to buy a bunch and that's not working out for me.

Piggy back them!  Search here for piggy backing.

[R.G.]

Welcome to the statistics of semiconductor manufacturing.

When you order a batch from one supplier, chances are you'll get devices that were once all part of a single semiconductor wafer, and they'll all be really similar. Unless you get parts which happened to come from two orders that the distributor made, and two wafers contributed to the bin. Or if they're really low, you may get leavings of several wafers from the bottom of the bin. It can happen all of those ways. Devices from the same wafer are very similar, different wafers can be quite different.

Buy some more from a different supplier to get a different wafer as a source.

I've had the other problem. The last batch of 3904s I measured were all uniformly about 250-300.

[chi_boy]

You guys should trade!   



Just kiddin'
Carry on.

[Maudibe]

Yo. Tweek it



http:www.doctortweek.co.uk

[zombiwoof]

the circuit I'm trying to build requires two 2n3904 with HFE close to 200.

I ordered 20 of the damn things and all of their hfe's are right around 110 with very little variation.

How am I to get the correct transistor hfe?  previous advise was to buy a bunch and that's not working out for me.

Try a different transistor that has hfe specs that are lower.   The actual number doesn't usually matter, as long as it's in the correct range and the correct type (germanium or silicon, NPN or PNP.

Al

[petemoore]

  RG wrote: "When in doubt, use 2n5088".
  Kind of general, and in general I find this transistor a very handy thing to have...in your hand when building a circuit that calls for NPN transistor.
  These HG/Ln [hi gain/low noise] transistors work great.
  ..unless your Fuzzface [low gain] or Bazz [darlington very high gain] or other build has some special requirement.

[DougH]

Buy some more from a different supplier to get a different wafer as a source.

If all else fails, keeping buying!! 

Sorry, R.G... That just struck my funny bone... 

[MikeH]

Yo. Tweek it



http:www.doctortweek.co.uk

I don't get it- is this spam?

[sundgist]

Yo. Tweek it



http:www.doctortweek.co.uk

I don't get it- is this spam?

/ missing after http, but I think this is what was meant.

What is special about ordering DIY parts from Doctor Tweek?

Doctor Tweek hfe tests transistors for your project, provides information and locates select parts. If you only want 10 of something then why be forced to buy 100? Things are packaged in useful 'project sized' quantities. Extra mojo available as standard.

[zombiwoof]

  RG wrote: "When in doubt, use 2n5088".
  Kind of general, and in general I find this transistor a very handy thing to have...in your hand when building a circuit that calls for NPN transistor.
  These HG/Ln [hi gain/low noise] transistors work great.
  ..unless your Fuzzface [low gain] or Bazz [darlington very high gain] or other build has some special requirement.

But is he going to be able to find a couple of 2N5088's that are around 200 hfe, which is what he needs?.  As you mention, those are high gain trannies.

Al

[MikeH]

Yo. Tweek it



http:www.doctortweek.co.uk

I don't get it- is this spam?

Ahh... I thought it was just someone randomly promoting their site.   
/ missing after http, but I think this is what was meant.

What is special about ordering DIY parts from Doctor Tweek?

Doctor Tweek hfe tests transistors for your project, provides information and locates select parts. If you only want 10 of something then why be forced to buy 100? Things are packaged in useful 'project sized' quantities. Extra mojo available as standard.