I am trying to calculate the hFE of a BC108 transistor using a tutorial book. One of the exercises is to measure the current at the collector output based on the current input at the base.
ie 5ua at base gives x at collector
10ua at base gives x at collector
upto 100ua and then plotting these on a graph for loadline etc
The tutorial states to set a bench top psu to 5v to keep constant voltage at the collector. I havent got one of these yet (I will build my own soon as my first proper project) so am taking the collector voltage from the circuit supply voltage (9v) and a 1k pot set to 5v.
My question : Is using a 1k pot set to 5v going to give me a different set of results on the above compared to using a psu voltage ie in terms of collector current. I can calculate the current through the 1k pot and change that to alter the current but what about a bench top psu, what would that do the current at the collector, would I have to put a resistor in series with it to give me a set current?
Secondly when I have calculated the hFE gain and the transistor is swapped with a different one would I have to do this again, especially if my circuit was beta specific? I have read that the hFE can vary considerably on each device. And if so how do factory processed boards compensate for this?
thanks
Graham
ie 5ua at base gives x at collector
10ua at base gives x at collector
upto 100ua and then plotting these on a graph for loadline etc
The tutorial states to set a bench top psu to 5v to keep constant voltage at the collector. I havent got one of these yet (I will build my own soon as my first proper project) so am taking the collector voltage from the circuit supply voltage (9v) and a 1k pot set to 5v.
My question : Is using a 1k pot set to 5v going to give me a different set of results on the above compared to using a psu voltage ie in terms of collector current. I can calculate the current through the 1k pot and change that to alter the current but what about a bench top psu, what would that do the current at the collector, would I have to put a resistor in series with it to give me a set current?
Secondly when I have calculated the hFE gain and the transistor is swapped with a different one would I have to do this again, especially if my circuit was beta specific? I have read that the hFE can vary considerably on each device. And if so how do factory processed boards compensate for this?
thanks
Graham