transistor test circuit

[gzifcak]

what kinds of opamps are ok for this? what does rail-to-rail mean? can i use a 741 or tl072?

[Guest]

with respect to an opamp rail to rail refers to the
ability of the input or output to operate at any point between
ground and the power supply voltage

both the 741 and tl072 can only get within 3 or 4 volts of the power
supply before the inputs and outputs clip

for the beta meter shown the opamp needs to get within 2 volts or
so of the power supply
so a rail to rail isnt strictly necessary but will make life easier

also for the beta meter to be accurate
the input impedence of the opamp needs to be high
and the input offset voltage and offset currents need to be low
so the 741 wont work as well
but the tl072 would be adequate in these respects

[gzifcak]

thanks for the info.
i can't quite tell from the datasheet, but i think it looks like half of a lm324 would work?
thanks
greg