Transistor NPN, PNP

Transistors are semiconductor devices used as amplifiers, as the circuit breaker and connecting (switching), voltage stabilization, signal modulation, or as other functions. Transistor can act like an electric faucet, where according to input current (BJT) or voltage input (FET), which allows electrical conduction of the circuit is very accurate source of electricity. BJT (Bipolar Junction Transistor) is one of the two types of transistors. How a BJT can be imagined as two diodes are positive or negative terminal packed, so there are three terminals. The third terminal is the emitter (E), collector (C), and base (B). FET is divided into two families: Junction FET (JFET) and Insulated Gate FET (IGFET) or also known as Metal Oxide Silicon (or semiconductor) FET (MOSFET). In contrast to the IGFET, the JFET gate terminal forming a diode with the channel (semiconductor material between the Source and Drain). In its function, this makes N-channel JFET to be a solid-state version of the vacuum tubes, which also forms a diode between the grid and cathode. And also, both (JFET and vacuum tubes) work in "depletion mode", both have a high input impedance, and they conduct electrical current under the control of the input voltage.
Bipolar transistors are used as electronic switches and amplifiers in digital electronic circuits. Transistor has 3 terminals. Transistors are usually made of silicon or germanium material. Three different leg forming a bipolar transistor are emitter, base and collector. They can be combined into NPN or PNP type which became one as a three-leg transistor.

BJT (Bipolar Junction Transistor)

NPN transistor, providing a positive voltage from the base to the emitter, causing the collector to emitter connections connected short, which causes the transistor active (on). Providing a negative voltage or 0 V from the base to the emitter causes the open collector and emitter, called the transistor die (off).

In the PNP transistors, providing a negative voltage from the base to the emitter of this transistor turns on (on). And provide a positive voltage or 0 V from the base to the emitter of this will make the transistor die (off).

JFET (Junction FET)

N-channel JFET to be a solid-state version of the vacuum tubes, which also forms a diode between the grid and cathode. And also, they (JFET and vacuum tubes) work in "depletion mode", both have a high input impedance, and they conduct electrical current under voltage control input.N-channel FET as an example: in the depletion mode, the gate is negative compared to the source , while the enhancement mode, the gate is positive. For both modes, if the gate voltage is made more positive, current flow between the source and drain will increase.


For P-channel FET, the polarity-reversed polarity. Most of the enhancement type IGFET is fashion, and almost all JFETs are depletion mode type.

FET is divided into two families: Junction FET (JFET) and Insulated Gate FET (IGFET) or also known as Metal Oxide Silicon (or semiconductor) FET (MOSFET). FET is further subdivided into type enhancement mode and depletion mode. Mode indicates the polarity of the gate voltage compared to the source when the FET conducts electricity.