There is a lot of 40 transistors marked as:
BC550
C K7A
(no logo)
I spent part of the morning matching them in pairs of similar Vbe for a constant current.They were all tested diode-connected (collector to base). No news here.
When trying to measure Ic for a constant Ib of 0,107 mA, found that no matter what Vb I applied to Rb (or leaving in the air), Ic was a steady 34 mA and transistor was rather warm.
After two hours checking everything, and contradicting what the datasheet shows, I reversed the pins (easy because base is the middle pin) and everything started to be "normal" with an Ic of 25 mA only when +9 V was applied to the base resistor. Otherwise, Ic = 0 mA.
Recalling that my DMM has hFE measurements, I got some credible value of 210 appr only when reversing the pins as above.
Further tests with a LED confirmed that something is going wrong: in the datasheet condtion, if I apply +9V to Rb and then leave it in the air, the LED stays dimly ON.
Reversing pins, LED switches ON and OFF as expected.
Last tests I did just for few of them. I had enough for he day.
Faked or failed ones sent to market expecting an idiot like me buying them?
BC550
C K7A
(no logo)
I spent part of the morning matching them in pairs of similar Vbe for a constant current.They were all tested diode-connected (collector to base). No news here.
When trying to measure Ic for a constant Ib of 0,107 mA, found that no matter what Vb I applied to Rb (or leaving in the air), Ic was a steady 34 mA and transistor was rather warm.
After two hours checking everything, and contradicting what the datasheet shows, I reversed the pins (easy because base is the middle pin) and everything started to be "normal" with an Ic of 25 mA only when +9 V was applied to the base resistor. Otherwise, Ic = 0 mA.
Recalling that my DMM has hFE measurements, I got some credible value of 210 appr only when reversing the pins as above.
Further tests with a LED confirmed that something is going wrong: in the datasheet condtion, if I apply +9V to Rb and then leave it in the air, the LED stays dimly ON.
Reversing pins, LED switches ON and OFF as expected.
Last tests I did just for few of them. I had enough for he day.
Faked or failed ones sent to market expecting an idiot like me buying them?
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