EE 238 MODULE 5

is generally a three terminal device which could be used in applications wherein bipolar junction transistors are used.

It is a _________ device as compared to a BJT which is a current controlled device.

The term_____ is used because for FETs, an electric field established by the carriers controls the conduction path of the output current without the need for direct contact between the input signal parameters and the output signal parameters.

It is a ____ device because current flow is only _____ on either electron flow (n channel) or hole flow (p channel).

BJT is a _____ device because current flow is always dependent on electron flow (n material) and hole flow (p material).

FETs have very high ____ (1 Mohm to hundreds of Mohm or higher), because the p-n junction at the input is operated in the reverse biased condition (for JFET), the gate is insulated (for MOSFET), or the gate has a

Junction field effect transistor (JFET), which has two types:

Metal oxide semiconductor field effect transistor (MOSFET) also called Insulated Gate FET or IGFET, which has two types:

Metal semiconductor field effect transistor (MESFET), which has two types:

Commercial MESFETs are typically made up of?

JFETs have three terminals:

is used to control the flow of current flowing through the drain and the source.

is the same as the source current. Both currents flow through the channel of the FET.

• The drain and the source are connected to both ends of

The drain current and source current are

Drain and source current flows

made up of two materials which are internally connected

The channel is sandwiched between

If the depletion region increases in width, the width of the channel decreases, and

Decrease in width of the depletion region results to

The width of the depletion region can be increased

Thus the drain current and source current can be controlled by changing the

For an n-channel JFET - When voltage between the gate and source (VGS) is 0 volt, and the voltage between the drain and the source (VDS) is positive at the Drain, the following conditions exist:

Conventional current flows from Drain to Source through the channel, and the current is only

Drain current (ID ) is equal to

When Drain to Source voltage (VDS) increases, Drain current (ID ) and Source current (IS )

When VDS increases beyond VP , Drain current (ID ) does not increase and practically remains at a constant saturation level called IDSS

When Drain to Source voltage (VDS) increases, Drain current (ID ) and Source current (IS ) also increase until VDS reaches the

the Drain to Source resistance is approaching an “infinite” value, as any increase in VDS

As the Drain to source voltage (VDS) increases beyond Vp, the region of close contact between the two depletion region

– IDSS is the maximum Drain current (Source current also, ID=IS ) for the JFET when VGS = 0 volt and VDS > |VP |, as long as VDS does not reach

When VDS reaches the maximum allowed value (breakdown voltage – VDS max )

For low values of VDS (VDS < VP ) , resistance from drain to source is relatively

Gate current (IG ) is practically equal to _____ because the p-n junctions are reverse biased.

– For p-channel JFET, the same conditions exist, except the polarity of the Drain to Source voltage (VDS) is ______, and the direction of the Drain current (IDS) is also ________.

The Drain current is typically controlled by

When VGS is more negative than the Source (for n-channel) and the Drain to Source voltage (VDS) is positive at the Drain

The depletion region between the Gate and the Source is

As the Gate to Source voltage (VGS) becomes more negative at the Gate, the saturation level of the Drain current

The characteristic curve of JFET has three regions which are

Others call the saturation region as

Others include another region called cutoff region at which