Transistor is a three terminal device. Its shape may differ with applications.
It depends on the transistor, you just have to look at the data sheet for the transistor.
uni junction transistor
A silicon transistor is a transistor made of silicon.
Similar to a 2N3906 PNP transistor
I believe that is resistor transistor technology TTL transistor transistor logic
It depends on the transistor, you just have to look at the data sheet for the transistor.
The 7812 is not a transistor. It is an integrated circuit, a voltage regulator designed to regulate an input voltage down to 12 volts output. It typically comes in a TO-220 case, and has three leads, so it sure does look like a transistor though!
A transistor acts like a resistor when Gate is connected to Source.
No. A diode is not like a transistor, and a transistor is not like (two) diode(s). Taken in isolation, the emitter-base and collector-base junctions of a transistor appear to be diodes, but they are coupled together so that the base-emitter current affects the collector-emitter current.
uni junction transistor
It looks like an Italian 'transistor'.
An NPN transistor must be biased with a positive voltage in order to "turn on". A silicon transistor must have at least .07 volts on its base to start current flow from the collector to the emitter of the transistor. Some transistors have different biasing voltages. Like a germanium transistor will "turn on" at .02 volts.
A transistor is not a diode. It is also not a pair of back to back diodes. Two diodes connected back to back will not function like a transistor because their junctions are not in close proximity like they are in a transistor. The only reason for "thinking" that a transistor is "like" a pair of back to back diodes is for purposes of quick go-nogo testing with a multimeter, but that will only assess open, short, and leakage status, as well as polarity, but not any of the more useful things, such as hFe.
A: A FET has a very hi impedance it requires mostly potential as opposed to current like a transistor does,
work like on off switch!!
A silicon transistor is a transistor made of silicon.
A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A simple illustration below. IIIIIIII IIIIIIII ..I I I ..I I I ..I I I