Electron Devices: Chapter 5: Field Effect Transistors

Drain Current Equation of JFET

Home | Department: ECE Department | Ist Year | Subject: Electron Devices |

Question: 1. Write the equation for drain current of JFET.

Current Equation

• In a transfer characteristics we have seen that the relationship between the drain current I_D and gate to source voltage V_GS is non‒linear. This relationship is defined by Shockley's equation

……….. (5.8.1)

• The squared term of the equation will result in a non‒linear relationship between I_D and V_GS producing a curve that grows exponentially with decreasing magnitudes of V_GS.

• In equation (5.8.1) I_D represents saturation drain current. I_DSS is the value of I_D when V_GS = 0, and V_P is the pinch‒off voltage. Differentiating this expression we get,

…………..(5.8.2)

• From expression (5.8.1) we also have,

………… (5.8.3)

• Substituting this value in equation (5.8.2) we have,

………. (5.8.4)

• When V_GS = 0, g_m = g_mo then from equation (5.8.2).

g_m = ‒2I_DSS / V_P

………. (5.8.5)

• Therefore, from equations (5.8.2) and (5.8.5)

………. (5.8.6)

• The equation (5.8.4) shows that g_m varies as the square root of the saturation current I_D and equation (5.8.4) shows that g_m decreases linearly with increase of V_GS.

Review Question

1. Write the equation for drain current of JFET.

Electron Devices: Chapter 5: Field Effect Transistors : Tag: electronics : - Drain Current Equation of JFET

Home | Department: ECE Department | Ist Year | Subject: Electron Devices |

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Electron Devices: Chapter 5: Field Effect Transistors

Field Effect Transistors - Symbol, Features, Classification

Construction of n-Channel JFET

Construction of p-Channel JFET

Operation of p-Channel and n-Channel JFET

Characteristics of JFET

JFET: The Pinch-off Voltage

Characteristics Parameters of JFET

Drain Current Equation of JFET

Comparison of BJT and FET

Applications of JFET

MOSFET

Depletion MOSFET (D-MOSFET) - Construction, Operation, Characteristics, Parameters, Type, Symbols

Enhancement MOSFET (E‒MOSFET) - Construction, Operation, Characteristics, Circuit Diagram, Parameters, Type, Symbols, Example Solved Problems

Channel Length Modulation in MOSFET

Comparison of MOSFET with JFET

Comparison of D-MOSFET and E-MOSFET

Comparison between N-Channel and P-Channel MOSFET

Comparison between N-channel and P-channel JFET

Comparison of BJT with MOSFET

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CMOS - Advantages, Disadvantages, Applications, Basic Operation as an Inverter

Field Effect Transistors: Important Example Solved Problems - Electron Devices

Field Effect Transistors: Two Marks Important Questions and Answers - Electron Devices

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