JFET - Types, Construction ,Working, and Biasing

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”.