- #1
fog37
- 1,568
- 108
Hello Everyone,
I would to ask you for a couple of clarifications if possible:
fog37
I would to ask you for a couple of clarifications if possible:
- I understand that a NPN transistor has 3 legs (emitter, base and collector) and that if a very small current goes from the base to the emitter (current ##I_{be}##, the transistor will be turned ON and a larger current, called collector current, will go from the collector to the emitter. The transistor is essentially an electronic switch. That said, I would think that a NPN transistor is a current-controlled device since a nonzero, small (not too small) current must pass from the base to the emitter. The presence of a voltage ##V_{be}## between the base and the emitter is not enough to turn the transistor on. A current must exist On the other hand, FET transistors, instead, seem to only require the presence of a voltage and don't draw a current to turn the transistor on. Is that correct?
- A transistor, whatever it may be, can be used as a switch (completely ON or OFF) and also as an "amplifier". When used as an amplifier, it creates an magnified replica of a smaller input signal that is applied to the base. The transistor essentially modulates a large DC signal to give it the same shape as the smaller input signal, correct? The input signal, and corresponding amplified replica, can be either digital or analog, correct? Or do different types of a transistors deal with digital and analog signals? Also, when talking about signal amplification, are we talking about current signals or voltage signals? Or does that distinction not matter since current and voltage can always be related by Ohm's law ##V=IR##?
fog37