I tried 20k , does not work either...I dont get it , I tried 1K, 230k, 500k, now 20k, I should get closer somehow...that bloody p of s does not switch at all
from 5v, it barely goes to 4.5v
tried 10k also, it goes down to 3.8V...I already tried smaller values
double checked everything
I tried a 50k pot for Rb, it should switch
I tried with another 818 that has a different id on its back, even worst, no matter what, the output is always 5v
I'll go to the shop tomorow and try to find 2222 bjt
everytime I try this simple setup, it takes me forever to make it work
I can also go with inverters I have but they are hex inverters, what a waste
a bjt would have been more elegant....
thanks anyway
With a 5V supply and a 1k load then the collector current is almost 5mA when the transistor is saturated. The "calculator" you used is completely wrong. The datasheet for your transistor and all little transistors shows a base current that is 1/10th the collector current for proper saturation.
You mentioned TTL. It has an output high of only about 3.5V when it has no load. The input of a TTL gate or inverter has almost no input current when it is high. Try an Rb that is (3.5V - 0.7V)/0.5mA= 5.6k ohms.
You don't need 100mA, not sure whether the transistor
you piked is good for 100mA anyhow but you need only
5mA or so. Pick a 1K pullup (Rc) and a 4.7K, 4.7K base
divider network (so threshold is ~ TTL 1.4V) and there
is your forced beta of 10-20.