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#1
10-10-2006, 05:49 PM
 Steve1992 Senior Member Join Date: Apr 2006 Posts: 100
Transistor HFE & data sheets

With reference to 'HFE Classification' on pdf.

There are 3 classes of BC548; postfix A,B,C.

If my circuit had a base current was 150uA and collector current 40mA (common-emitter config.)
HFE = 266.

Would it matter if I chose BC548A, ..B or ..C transistor?

Steve
Attached Files
 BC548.pdf (44.9 KB, 52 views)
#2
10-10-2006, 07:00 PM
 Papabravo Senior Member Join Date: Feb 2006 Location: Michigan, USA (GMT-5) Posts: 5,782

Well of course it matters. Where you need to start is from the following two points.

#1 - Never design a circuit which depends on a specific value of hFE
#2 - Understand that the ranges represent plus and minus three sigma points on a normal distribution. This means that 99% of all transistors in the population will have an hFE inside the range. That leaves 1% with values that are either higher or lower.

We live in a statistical world where a range of values is equivalent to giving a mean and a variance. The proper way to design a circuit is to be insensitive to the actual value of hFE, or to at least funtion correctly over a suitable range. If you don't know how to do that then you need to ask more questions.

 Tags data, hfe, sheets, transistor

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