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Old 5th October 2004, 06:10 AM   #1
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Default 2SA1145 Ic

Hi,

Is the lowish Ic rating of -50mA for these transistors a conservative rating at all? Any chance if used as a switch I could push them a bit beyond that, to say 60 or 70mA?

Thanks
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Old 5th October 2004, 06:25 AM   #2
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There may be some headroom in the specs, but you don't use a 50ma part when you plan to have 50ma of current. ANy more than you would drive your car around revved to the redline.

Do you need PNP?

If you need 60ma current rating for the circuit, you should use a 100ma or larger transistor. Give it some breathing room.

There are other parts that are cheap. I have a bag of MPSA56 for general small switching use - 80v, 500ma, and cheap.

Go to www.jameco.com or www.mouser.com and look up:
2N4403, MPSA56, 2N3906

Or check your favorite source for Japanese types for:
2SA1015, 2SA933, 2SA733

All of these are cheap adn useful in many places.
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Old 5th October 2004, 06:35 AM   #3
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Hi Enzo, thanks for the help, that's more than I expected !


What's going on is I've got a little prototype on the go and in testing I ran short of 2n3906 transistors, I need PNP and it seems I need at least ~80mA to do the job I need.

So I was just hunting down some parts on old/useless circuit boards and those are the only PNP's I found, from my old pioneer amp.

I just woke up a little bit though, I can use the 2SA1145 pnp's in my differential input pair since it operates at low current they'll be perfect, and that will free up two 3906 for use elsewhere

I'm scrounging because it would take over a week to order anything.

I seemed to recall someone mentioning pushing them a bit beyond before while tweaking their amp and others saying it was OK to do it so I thought I'd ask, of course I could also have been just trying convince myself.

Thanks for the info.
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Old 5th October 2004, 01:58 PM   #4
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Why would you want to use a very linear transistor as a switch???? They work well in the voltage gain stage of a typical amp. Which explains why they are there.

Jocko
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Old 5th October 2004, 08:10 PM   #5
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Hi,

Just because a switch is what I need, that's all.

Anway no need to worry, it wasn't up for the task. I swapped it around so the the 2SA1145's are now in the differential input pair working at 1.5mA in a linear fashion
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