We are using the BC856ALT1G in our products. Below is the datasheet from ON Semiconductor.
How much does hFE decrease at -40C (low temperature)? How do I calculate the hFE value at low temperature?
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\$\begingroup\$ It will drop a lot. Designing based on hfe is bad. \$\endgroup\$– Matt YoungMay 22, 2017 at 4:44
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\$\begingroup\$ CMOS works better cold, BJT's work better hot.. So use CMOS OP AMP and/or MOSFET \$\endgroup\$– Tony Stewart EE75May 22, 2017 at 5:41
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\$\begingroup\$ my answer shud read -50%hFE minimum at -50'C unless saturated, then not significant, then use de facto Ic/Ib=10 \$\endgroup\$– Tony Stewart EE75May 23, 2017 at 17:44
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\$\begingroup\$ I hope u got your answer \$\endgroup\$– Tony Stewart EE75May 24, 2017 at 6:25
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2 Answers
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This is typical relationship for a BJT , the lowly but still great PN2222A that costs less than a penny.
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The temperature coefficient for Beta is called NTB and is given only in SPICE files by OEM
In every case I have seen so far including your device, it is a positive temp coefficient. Although @jonk has more data on this, I have yet to see evidence to the contrary.
For more details https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-quirks/
answered May 22, 2017 at 5:46
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\$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$ May 24, 2017 at 11:09
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If we have a look at theNexperia datasheet for their similar part number, we can get an idea of what is likely. Of course chances are better it might resemble the 'typical' curves if you specify the Nexperia part. Chances are also better if you operate near the middle of the curve in Ic.
answered May 22, 2017 at 7:25