# Question: What Is Source And Drain In Transistor?

## Can current flow both ways through a Mosfet?

Yes it does conduct in either direction.

Due to the body diode, most discrete MOSFETs cannot block in the reverse direction, but the channel will conduct in either direction when the gate is biased “on”.

If you want to conduct and block in both directions you need two MOSFETs in series..

## Are MOSFETs bidirectional?

The MOSFET is a bidirectional device, from the point of view that the terminals called the ‘Source’ and ‘Drain’ can be interchanged. … Any of the other two can be chosen as the SOURCE, and the gate voltage with respect to that terminal is made greater than the threshold voltage for the device.

## How is drain resistance calculated?

Answer: The resistance of a MOSFET operated in the linear mode is given by: R = VDS/ID where the drain-source voltage and the drain current are related by: The resistance therefore equals: R = L/ ( mn Cox W (VGS – VT )) = 10-4 /(300 x (3.9 x 8.854 x 10-14/ 10-6) x 20 x 10-4 x (5-1.5)) = 321.8 Ohm.

## 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.

## How many types of FET are there?

There are two main types of field effect transistor, the Junction Field Effect Transistor or JFET and the Insulated-gate Field Effect Transistor or IGFET), which is more commonly known as the standard Metal Oxide Semiconductor Field Effect Transistor or MOSFET for short.

## What is the difference between BJT and FET?

BJTs and FETs are two different kinds of transistors and also known as active semiconductor devices. … The major difference between BJT and FET is that, in a field effect transistor only majority charge carries flows, whereas in BJT both majority and minority charge carriers flows.

## What is n well and p well?

The N-well / P-well technology, where n-type diffusion is done over a p-type substrate or p-type diffusion is done over n-type substrate respectively. The Twin well technology, where NMOS and PMOS transistor are developed over the wafer by simultaneous diffusion over an epitaxial growth base, rather than a substrate.

## What is drain resistance?

Drain resistance is basically the resistance offered by the drain terminal of the fet device. its the ratio of change in drain to source voltage to the change in drain current at a constant gate to source voltage.

## Why substrate is used in Mosfet?

The area between the source and drain is called substrate and is lightly doped with the opposite dopant, p-type. In the boundary between n-type and p-type materials, the electrons from the n-type material quickly spread to the p-type material by diffusion, filling the holes in it.

## Is Mosfet a transistor?

MOSFET is a kind of field effect transistor (FET) that consists of three terminals – gate, source, and drain. … The voltage that is applied across the gate controls how much current flows into the drain. MOSFETs are available in two types, “p-channel” and n-channel”.

## Why pinch off voltage is negative?

This is because a negative voltage on the p region under the gate causes the depletion region to expand and eventually deplete the entire channel. When the channel is depleted of charge conduction stops. Pinchoff voltage in an n-channel JFET is most often negative.

## Why gate current is zero in FET?

Zero gate current in jfet. … For instance in a n-channel JFET the channel is n-type material and the gate is p-type, so the gate voltage must be zero or negative with respect to the source. A negative voltage causes the current through the channel to decrease.

## Are source and drain interchangeable?

Source and Drain are interchangeable in schematic/layout. But once fabricated in silicon, they will be slightly different because of the doping process which is angular (not 90degrees) with respect to the silicon substrate, this makes the two terminals slightly different.

## What is drain current FET?

In the usual MOSFET theory, the drain current flow is predicted to be zero for gate voltages below VT. In actual devices, this is seldom true. The drain current for gate voltages below VT is known as the subthreshold current.

## Why P substrate is used?

The answers here are correct but there is a very important additional reason why a p-type substrate is preferred. NMOS transistors are faster than PMOS transistors all else being equal. To make n channel MOS, the well must be p type. To get the maximum electron mobility, the p should be as lightly doped as practical.

## What is drain source voltage?

• Drain-Source Voltage (V. DS. ): controls the electric. field that drifts the inversion charge from the source. to drain.

## Is drain current equal to source current?

Source is the supplier of electrons , which goes out of DRAIN. Because the gate resistance to either the drain or source has nearly infinite resistance. So no drain current. The source and drain currents therefore are equal but opposite.

## What is source and drain?

source (S), through which the carriers enter the channel. Conventionally, current entering the channel at S is designated by IS. drain (D), through which the carriers leave the channel. Conventionally, current entering the channel at D is designated by ID. Drain-to-source voltage is VDS.

## Why P substrate is lightly doped?

O). The p-type doped substrate is only very lightly doped, and so it has a very high electrical resistance, and current cannot pass between the source and drain if there is zero voltage on the gate. … When the gate electrode is positively charged, it will therefore repel the holes in the p-type region.

## What is the symbol of Mosfet?

The line in the MOSFET symbol between the drain (D) and source (S) connections represents the transistors semiconductive channel. If this channel line is a solid unbroken line then it represents a “Depletion” (normally-ON) type MOSFET as drain current can flow with zero gate biasing potential.

## What is source and drain in Mosfet?

MOSFETs have three pins, Source, Drain, and Gate. The source is connected to ground (or the positive voltage, in a p-channel MOSFET), the drain is connected to the load, and the gate is connected to a GPIO pin on the Espruino.