### Author Topic: Is the BC517 transistor a suitable replacement for the MPS-A13 transistor?  (Read 2906 times)

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#### ee90099

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##### Is the BC517 transistor a suitable replacement for the MPS-A13 transistor?
« on: October 14, 2016, 04:04:14 pm »
Hi everyone,

I've been working on restoring an old Gotlieb pinball machine and had a few questions about hfe of transistors. The original machine used a MPSA13 transistor which is no longer readily available and I need to find a substitute part. After searching digikey, I believe that a BC517 transistor would be a suitable replacement. However, one of the things that I'm having a hard time understanding is the hfe on the datasheets. The MPSA13 shows a minimum/maximum hfe of 5,000 and 10,000 at Ic=10ma and Ic=100ma while the BC517 has a minimum hfe of 30,000 at Ic=20mA. I typically look at the curves when determining hfe, and the graphs for each transistor show an hfe of 100 at Vce=5V and Ic=10mA. So where are these high gains that are shown in the datasheet tables coming from?

Here's a link to the two datasheets:

https://www.fairchildsemi.com/datasheets/BC/BC517.pdf

https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/MPSA13Rev2007.pdf

Also, does anyone see any issue that I've missed with using the BC517 in replacement of the MPSA13?

#### Keicar

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##### Re: Is the BC517 transistor a suitable replacement for the MPS-A13 transistor?
« Reply #1 on: October 14, 2016, 04:21:39 pm »
If you look at the Y-axis label, you'll see a '(K)' on the end - so the Hfe value you're reading as 100 is actually 100,000 - which is exactly as you'd expect for a darlington pair.

#### ee90099

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##### Re: Is the BC517 transistor a suitable replacement for the MPS-A13 transistor?
« Reply #2 on: October 14, 2016, 04:25:27 pm »
Thanks

Anything else dumb that I've missed?

#### Keicar

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##### Re: Is the BC517 transistor a suitable replacement for the MPS-A13 transistor?
« Reply #3 on: October 14, 2016, 04:44:57 pm »
All good, I'm no expert myself. I think that both of these part numbers are sorted from the same production process (hence the 'sourced from process 05' on both datasheets) - they're basically the same part. The lower gain ones are marked as MPSA13, the higher gain ones as MPSA14/BC517. Anyway, I'd imagine that for a switching application especially (as I suspect this may be), the precise gain values are of little consequence and the higher gain version could be substituted without a problem.

Smf