Mimimum base current for 2N3055

** You Q makes no sense.

Some context is ESSENTIAL !!

.... Phil

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That depends on what you want to do.

Minimum base current? You can probably feed it 10nA and get ~1uA from the collector... but that would be a pretty silly thing to do.

If you're looking at the same data sheet I down loaded then figure 2 shows typical current gain vs collecter current. (divide Ic by hfe and you have an estimate of the base current you'll need.) Unless you want to saturate the thing... then figure 3 is your friend.

As Phil and JF said, more context is needed if you want more specific advice.

George H.

Zero. Just leave the base disconnected.

If this answer frustrates you, re-read your question and ask yourself what other answer could be given.

--
Tim Wescott 
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Or if you mean direction, not just magnitude, then you can probably sink five or ten amperes out of it ("IB2 = -5A" or whatever), during reverse recovery of the B-E junction. It'll only last a couple microseconds though.

Tim

--
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You could feed it a negative current too.. minimum current to damage the E-B junction? Minimum current to burn off the bonding wire?

Yes I was torn between "zero" and some negative damage threshold.

I thought I saw something about 2N3055 being good for a low noise amplifier, which sounds ridiculous but could be related...

[...]

--

John Devereux

It's not a switching device, so the current into the base has a 'minimum' only in the sense that a hot device under bias leaks from the collector. So, to reliably turn OFF the transistor, you might need to sink 200 mA/beta at 25 C, 60Vce (that's circa 2 mA).

The specs on beta (also known as h_fe) are, of course, very loose; 20 to 70 at 4A, and there's temperature and collector-current variations in the charts.

My source here is the RCA file #145, dated August 1966 (that's the most complete data sheet I know of for this part).

Large power devices, particularly those with star or Christmas tree layouts, have low rbm, thus low noise. ...Jim Thompson

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Zero.

If you're using the collector to switch some load on and off, at X amps, you need to jam in maybe X/20 or even X/10 amps into the base. Look at the data sheet for details. The more base current, the less "on" resistance of the collector switch action.

Mosfets are easier to drive. Just apply some voltage (like 10v maybe) to the gate to turn them on, zero to turn them off. The gate current is minute.

--

John Larkin         Highland Technology, Inc 

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Finally someone who can actually understand the question.

I did that on a physics exam in college. The question didn't eliminate the trivial answer. The prof thought I was being a smartass and I thought he was throwing out one of his famous trick questions. It did seem a little odd that zero being the answer to that question made the next quarter of the exam result in zero answers, also (a bit much for a trick question but it was correct). He was a bit miffed but gave me credit on the exam. It was a correct answer.

I think you're talking about the Beta(Hfe) curve.. should be a chart in the spec showing at what point the transfer is at the max.

That's an old part and many published data sheets.

Some one told me once that a 3055 was just a ball park component, soured from various other high power transistors that may have not met their mark. If that being the case, it's possible you may find large noticeable differences from lot to lot.

Jamie

"George Herold" snipped-for-privacy@gmail.com

Minimum base current? You can probably feed it 10nA and get ~1uA from the collector

** That is VERY unlikely - the Hfe of power BJTs falls at low ( and high) currents so much so that most data sheets do not spec it below about 50mA Ic.

Long time ago, I was checking the Hfe of a batch of Motorola MJ4502s - I came across one that tested 450 at 1mA Ic.

I thought of framing it....

.... Phil

gh)

 -  I

Well OK, I've been using these TIP31/32 's in to220 pacs as temp sensors, diode conected transitors. At 10nA of collector current the ideality is starting to fall off, 100nA looks OK. I figured a higher power BJT might be 'good' to 1uA.

Have you measured a 3055 at 1uA? (I did say probably..)

George H.

According to urban legends, some manufacturers even branded failed VHF transmitter transistors as 2N3055 and caused huge stability problems in existing circuits :-)

So if the original specification called for fT > 0.8 MHz, so it would be OK to sell a transistor with fT > 500 MHz as long as the other requirements were met.

That's Icbo to all you sports fans out there.

RL

Wasn't he traded to the minor leagues?