Performance of MOSFETs: Characteristic of Capacitance

Capacitance characteristics of Ciss, Crss and Coss are important factors affecting switching characteristics of MOSFET.

Ciss: input capacitance (Ciss  = Cgd + Cgs)

 ⇒Sum of gate-drain and gate-source capacitance: It influences delay time; the bigger the Ciss, the longer the delay time.

Crss: Reverse transfer capacitance (Crss  = Cgd)

 ⇒Gate-drain capacitance: The bigger the Crss, the more the characteristic of drain current rising deteriorates, which is disadvantageous for MOSFETs’ loss. Low capacitance is needed to drive at high speed.

Coss: Output capacitance (Coss = Cgd + Cds)

 ⇒Sum of gate-drain and drain-source capacitance: It influences turn-off characteristic, and loss with light load. In the case of large Coss, turn-off  dv/dt decreases, which is advantageous for noise. But loss with light load increases.

Capacitance model of MOSFET
Fig. 3-11(a) Capacitance model of MOSFET
Typical capacitance characteristic of MOSFET
Fig. 3-11(b) Typical capacitance characteristic of MOSFET

Chapter III : Transistors

Types of Transistors
Bipolar Transistors (BJTs)
Bias Resistor Built-in Transistors (BRTs)
Junction Field-Effect Transistors (JFETs)
Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)
Differences between BJT and MOSFET
Structure and Operation of MOSFET
MOSFET Performance Improvement: Decision Factors of RDS(ON)
MOSFET Performance Improvement: Approach to Low RDS(ON)
MOSFET Performance Improvement: Super-Junction MOSFETs (SJ-MOS)
Summary of MOSFET Features by Structure
Performance of MOSFETs: Drain Current and Power Dissipation
Performance of MOSFETs: Avalanche Capability
Performance of MOSFETs: Safe Operating Area(or Area of Safe Operation)
Insulated-Gate Bipolar Transistors (IGBTs)
Operation of Insulated-Gate Bipolar Transistors (IGBTs)
Performance Improvement of IGBTs: Evolution of Vertical Design
What are RC-IGBTs and IEGTs?
Application of IGBTs
Comparison of Forward Characteristics of IGBTs and MOSFETs
Comparison of Transistors by Structure
Datasheets of MOSFET: Maximum Ratings
Datasheets of MOSFET: Electrical Characteristics
Datasheets of MOSFET: Capacitance and Switching Characteristics
Datasheets of MOSFET: Body Diode

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