2N3904 experiment

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Some eye opening results after some transistor testing 

I needed two NPN transistors
-one with lower beta/hFE than 2n3904 (hFE 173)
- one with higher

So I started testing and the first victim mps222A tested hFE 175 

So next I pull out this billy badass radio shack TO-220 TIP 3055.  I'm like oh hell yeah it's on now 
It tested 11 hFE.    retested and got 12 

Tested ecg128 and get a 171....ok keep going 

So I had about ten of these puny 2n3391a and wow  tested hFE 419 


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Now obviously I'm lacking comprehension here I'm sure there is a reason for this and it should make sense.

Anyhow I have my test candidates 

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And the results are in with some conclusions
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When a small hFE transistor was placed in the circuit the voltage drop across the collector resistor was very small or very low collector current

When a large hFE transistor was placed in circuit there was a big voltage drop across the collector resistor ie much greater collector current

Meanwhile...base current remained pretty much constant

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So I'm thinking that the base is like a rock.  In response to that I was gonna post Bob Seger like a rock...but I really like fire lake.

(I've been to Cold Lake but not Fire Lake)

[J M Fahey]

Vbe looks "like a rock" because it is being force fed throughn am high-ish resistor (100K)

As of the wide Hfe disparity:

small signal (preamp) transistors are optimized for high gain, they don´t worry about high current because they typically will be used around 1-2 mA or so.
Low dissipation also, 300-500mW (tops).

Power transistors on the contrary are optimized for POWER     , high dissipation (70 to 120W), high current (think 10-15 Amperes), etc.

*Everything* in this World is a compromise, so the heavy price paid is abysmal Hfe.

You will find than in all power Amps, power transistors are never used by themselves, *always* driven by a medium power driver transistor, in a Darlington or Quasi Darlington configuration, so their Hfe multiply.

For example my rule of thumb for 50-100W power amps I design is a 2N3055 (Hfe 10 @ 10A) driven by a TIP 31/32 (Hfe 40 @ 1A)) for a combined Hfe of 400, go figure.

I am very conservative (which is safe), in practice combined Hfe is quite higher, but that is a guaranteed minimum value.

Later I switched to power Darlingtons, TIP142/147 (which are a sort of Industry Standard, being also used by Fender Marshall Ampeg Laney Peavey Crate, H&Kettner which should mean something.

Guaranteed Hfe @ 10A is 1000, go figure.

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Thank you very much sir that was awesome 

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I know right now (I think) that all of this is gonna go together like a big 🗝� key lime pie I'm lust learning how to make the crust and missing the key ingredients 

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Ok thought I would wrap this one up.  Last set of experiments were same setup only now an emitter resistor was added. 

This was the first time I couldn't notice a trend maybe I should compare with the other configurations idk I'm still like a mindless zombie doing this stuff.

Anyhow wow an emitter with a resistor wiped out the tpi3055

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Ok I did notice something seems this was the first time base current took a hit.