Well.... yes, and. If you think of an NPN transistor as a current-operated switch (e.g. to drive an LED or relay), then you can have a pretty simple model of sa

Well.... yes, and. If you think of an NPN transistor as a current-operated switch (e.g. to drive an LED or relay), then you can have a pretty simple model of said NPN transistor. If you want to make a low-noise PIN diode photodetector amplifier with an op amp, you want to understand noise per root Hz, input offset voltages, variations with temperature, gain, frequency and phase response, and so much more. So, as is often the case in Engineering: It Depends...