31-12-2015, 09:03 PM
The AF118 is a real oddity. I don't think much has been written about it. Possibly because it wasn't that widely used.
Make, test, sort into bins has been done for many parts. Carbon composition resistors were routinely done this way, hence the nice (almost) geometric series of preferred values. Hands up those who have use 2N2926 transistors. With about 5 different hFe ranges. ISTR green sport were the higheset gain, followed by yellow. Did anyone actually use the lowest grades? Or BC108A/B/C. Or the horrendous variability of 2N3819 FETs which weren't selected and binned. Or BF245A/B/C FETs which were and hence much easier to work with.
It's quite possible that BC107 was simply BC108 selected for high VCBO. And BC109 simply BC108 selected for low noise.
Then there's the 2N3055 where you've really no idea what's inside. The original spec was so wide you could put almost any reject power transistor die in the package and theoretically meet spec. Except the ones with high fT would sing like canaries in some circuits.
Make, test, sort into bins has been done for many parts. Carbon composition resistors were routinely done this way, hence the nice (almost) geometric series of preferred values. Hands up those who have use 2N2926 transistors. With about 5 different hFe ranges. ISTR green sport were the higheset gain, followed by yellow. Did anyone actually use the lowest grades? Or BC108A/B/C. Or the horrendous variability of 2N3819 FETs which weren't selected and binned. Or BF245A/B/C FETs which were and hence much easier to work with.
It's quite possible that BC107 was simply BC108 selected for high VCBO. And BC109 simply BC108 selected for low noise.
Then there's the 2N3055 where you've really no idea what's inside. The original spec was so wide you could put almost any reject power transistor die in the package and theoretically meet spec. Except the ones with high fT would sing like canaries in some circuits.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
