What Is Difference Between FET And BJT?

What is the advantage of FET over BJT?

The advantages of FETs relative to BJTs are summarized as follows: FETs are voltage-sensitive devices with high input impedance (on the order of 107 to 1012 Ω).

Since this input impedance is considerably higher than that of BJTs, FETs are preferred over BJTs for use as the input stage to a multistage amplifier..

What are the types of FET?

Types of FET(1) Junction Field Effect Transistor (JFET) These JFET’s working is based on the channels formed between the terminals. … JFET Working. … (2) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) … MOSFET Types: … (1) Fixed Bias. … (2) Self Bias. … (3) Potential Divider Bias. … (1) Ohmic Region.More items…•

What are the disadvantages of FET over BJT?

FETs (and their ilk) are extremely sensitive to voltage spikes, especially the static discharge kind. These voltage fluctuations can easily puncture the junction and either weaken it, or destroy it. BJTs can also be harmed this way however they are considerably less sensitive to this issue.

What are the applications of FET?

FETs are widely used as input amplifiers in oscilloscopes, electronic voltmeters and other measuring and testing equipment because of their high input impedance. As a FET chip occupies very small space as compared to BJT chip, FETs are widely used in ICs.

What are BJT used for?

The main basic function of a BJT is to amplify current it will allow BJTs are used as amplifiers or switches to produce wide applicability in electronic equipment include mobile phones, industrial control, television, and radio transmitters. There are two different types of BJTs are available, they are NPN and PNP.

What is the symbol of Ujt?

The symbol of UJT is designed in such a way that arrow is bent and shown that it is in the direction towards the channel. It resembles of JFET. If the channel is made of the N-type then the terminal called emitter is of P-type and vice-versa. But the other type is rarely used.

Why FET is used instead of BJT?

MOSFET is used for POWER SUPPLIES and is efficient. whereas BJT is used in low power consuming devices like LED. BJT consumes more power as it is a current controlled device,it results in less efficient than mosfet. … MOSFET is efficient because its output depends on the input voltage and not input current.

Why Ujt is called unipolar?

All FETs can be called UNIPOLAR devices because the charge carriers that carry the current through the device are all of the same type i.e. either holes or electrons, but not both. This distinguishes FETs from the bipolar devices in which both holes and electrons are responsible for current flow in any one device.

What is the difference between Ujt and BJT?

BJT is a current controlled device, where as UJT is a voltage controlled device. … UJT is also known as “Double Base Diode” as it contains two bases; where as BJT contains three terminals namely, Emitter, Base and Collector.

What is the symbol of FET?

Junction FETs or JFETs were the first type of FET and these have a distinctive symbol showing the diode junction. Insulated gate FETs, including MOSFETs have circuit symbols that indicate the insulation on the gate. Obviously dual gate FETs have two gates and both need to be incorporated into the circuit symbol.

What is the principle of FET?

The FET controls the flow of electrons (or electron holes) from the source to drain by affecting the size and shape of a “conductive channel” created and influenced by voltage (or lack of voltage) applied across the gate and source terminals.

Why FET is so called?

FETs are special type of transistors which are controlled by the voltage applied across the input terminal called the ‘Gate’. The electric field produced due to this gate voltage controls the operation of the FET . Thus as they are dependent on the ‘field’ applied across their input ,they are called so.

What is quiescent operating point?

The operating point of a device, also known as bias point, quiescent point, or Q-point, is the DC voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied. A bias circuit is a portion of the device’s circuit which supplies this steady current or voltage.

Why BJT is called current controlled device?

BJT is a current controlled device because the output characteristics of BJT are determined by the input current. In a p-n junction i.e base-emitter junction in BJT the change in voltage (Vbe) is produced only after the change in base current.

What are the parameters of FET?

Parameters of JFET or Specifications of JFETGate Cut Off Voltage (VGS(off))Shorted Gate Drain Current (IDSS)Transconductance (gmo)Dynamic Output Resistance (rd)Amplification Factor (μ)

Which is better FET or BJT?

FETs offer greater input impedance than BJTs. This means that they practically draw no current and therefore do not load down the power circuit that’s feeding it. BJTs offer greater gain at the output than FETs. The gain (or transconductance) of FETs are smaller than for BJTs.

Why BJT is more noisy than FET?

BJT’s are noisier than FET’s. A BJT is having two pn junctions whereas an FET is having only one pn junction. Hence charge carriers will have to cross more depletion regions in BJT and hence the possibility of addition of thermal noise and minority charge carriers is much higher. … Hence less noisy.

Which type of switch is used in Ujt?

A unijunction transistor (UJT) is a three-lead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch. The UJT is not used as a linear amplifier.