The transistor is the semiconductor device that regulates, controls and amplifies electronic signals. Transistors are mainly divided into three types, which are:
- Bipolar junction transistor
- Field effect transistor
Among these two types, the junction field effect transistor is a type of field effect transistor which was first patented in 1945 by Heinrich Welker. The first working model of junction field effect transistors (JFET) was made in 1953. A junction field effect transistor, also known as JFET, is one of the simplest field effect transistors. In JFET, the current flow is due to most charge carriers, but it is unidirectional. Based on the current flow, there are two main types of junction field effect transistors, and they are:
- n-channel JFET
- p-channel JFET
Read More – Junction Field Effect Transistor
Important Questions with Answers
1. What are the applications of junction field effect transistors?
The JFET is widely used in different applications due to its extraordinary features. Some of them are:
- The junction field effect transistor (JFET) can be used as a switch, a chopper, or a buffer.
- The JFET is used in oscillatory circuits and cascade amplifiers.
- It can be used as a voltage control resistor, a high input impedance amplifier, a differential amplifier, a low noise amplifier, and a constant current source.
2. What is the advantage of junction field effect transistors?
Junction field effect transistors are low-power consumption devices. They have a very high impedance. In small sizes, they can be fabricated. They occupy significantly less space in electrical circuits because of their small size. JFETs have a negative temperature coefficient of resistance so they can possess high-temperature stability.
3. What are the two types of junction field effect transistors?
Junction field effect transistors can be categorised into two main classes, depending on the current flow source. And they are,
- n-channel junction field effect transistor (n-channel JFET)
- p-channel junction field effect transistor (p-channel JFET)
4. What are the types of field effect transistors?
Mainly, there are two main types of field effect transistors,
- Junction field effect transistor or JFET
- Metal oxide semiconductor field effect transistor or MOSFET
5. What are the disadvantages of JFET?
The primary disadvantage of JFET is that it has a very low gain-bandwidth product compared to traditional transistors. It has very low voltage gain due to short transconductance. And also, the performance of the JFET is impacted as frequency gains due to feedback by internal capacitance.
6. What is the full form of JFET?
The full form of JFET is a junction field effect transistor.
7. What is a semiconductor?
Semiconductors are a kind of material which has conductivity in between conductors that are generally metals and non-conductor or insulators, such as ceramics. Examples include gallium arsenide, cadmium selenide, silicon, and germanium.
8. What is a junction field effect transistor or JFET?
The JFET, or junction field effect transistor, is one of the most accessible field effect transistors. It has no PN-junction. Instead of a PN-junction, it has a thin part of high resistivity semiconductor material composing a channel of n-type and p-type semiconductor material, such as silicon. This channel allows most carriers to flow through with two ohmic electrical contacts at either end, called drain and source.
9. Describe the working of junction field effect transistors.
We can easily understand JFET’s working if we compare it with a garden hose tube. If there is no obstruction, water floats smoothly via the garden hose tube. If we squeeze the tube slightly, the water flow is delayed, exactly like how the JFET operates. Here, the tube hose is similar to JFET, and the water flow is comparable to the current floating via JFET. We could manage the current flow by assembling the current carrying channel according to our requirements.
10. How many diodes do junction field effect transistors contain?
The junction field effect transistor contains two diodes.
Practice Questions
- Explain the construction and working of junction field effect transistors.
- How many layers are in JFET? What is the saturation mode?
- How does the depletion layer become broader and narrower in JFET?
- What is the working principle of a junction field effect transistor?
- What is the symbol of JFET?
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