DC Current Gain on transistor

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mikro
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DC Current Gain on transistor

Post by mikro » Thu Nov 14, 2019 3:17 pm

Hey guys,

this is going to be one of the "I have no clue but need to solder it anyway" question. ;-)

I'm upgrading a CRT monitor and one part I need is a BC548B transistor. Impatient to wait for eBay or similar delivery I have visited a local electronics shop. They had only a BC548C. Looking at the specs: https://www.onsemi.com/pub/Collateral/BC546-D.PDF the only difference I can see is in the "current gain" characteristics - the C version has all values (min/typical/max) about twice as big.

Does the C version qualifies as a replacement for "B" ?

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exxos
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Re: DC Current Gain on transistor

Post by exxos » Thu Nov 14, 2019 3:59 pm

It really depends on what circuit it is in.

For easy example, If you have 1mA base current with a gain of 100, then you can switch 100mA C-E junction. Which is basically how amplifiers work. In case of audio, it probably won't matter much.

For SMPSU's, they normally have a gain of 10. So if you had a CE-current of 1A at 10 gain, then if you jumped to gain 50, then you would be pushing 5amps through C-E. In which case you would probably end in fire.

So while they are general purpose switches and may well be interchangeable, I really wouldn't recommend doing it unless you know exactly what consequences doing that will cause.
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mikro
Posts: 164
Joined: Mon Aug 28, 2017 11:22 pm

Re: DC Current Gain on transistor

Post by mikro » Thu Nov 14, 2019 4:53 pm

I'm glad I asked! Fire definitely doesn't sound as something I would like to see. I have ordered it online then.

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