JFET
is Junction gate field-effect transistor. Normal transistor is a current
controlled device which needs current for biasing, whereas JFET is a voltage
controlled device. Same like MOSFETs, JFET has three terminals Gate, Drain, and
Source.
JFET is an essential component for precision level voltage operated controls in analog electronics. We can use JFET as voltage controlled resistors or as a switch, or even make an amplifier using the JFET. It is also an energy efficient version to replace the BJTs. JFET provides low power consumption and fairly low power dissipations, thus improving the overall efficiency of the circuit. It also provides very high input impedance which is a major advantage over a BJTs.
There are different types of Transistor, in FETs family, there are two subtypes: JFET and MOSFET. , here will learn about JFET.
Types
of JFET
Same
like MOSFET it has two subtypes- N Channel JFET and P Channel JFET.
N
channel JFET and P channel JFET schematic model are shown in the image above.
The arrow denotes the types of JFET. The arrow showing to the gate denotes that
the JFET is N-channel and on the other hand the arrow from the gate denotes
P-channel JFET. This arrow also indicates the polarity of P-N junction, which
is formed between the channel and the gate. Interestingly, an English mnemonic
is this, that arrow of an N- Channel device indicates “Points in”.
