Transistors｜Basic
Total Gate Charge
What is Total Gate Charge (Qg)?
The Total Gate Charge (Qg) is the amount of charge that needs to be injected into the gate electrode to turn ON (drive) the MOSFET.
The unit of Qg is the Coulomb (C), and if the total gate charge is large, it will take time to charge the capacitor necessary for turning ON the MOSFET, increasing switching loss. The smaller this value, the lower the switching loss and the higher the switching speed that can be achieved.
Total Gate Charge and ON Resistance
As mentioned earlier, the smaller the Gate Charge the lower the switching loss. Also, the smaller the ON Resistance, the lower the power dissipation during operation.
However, the characteristics for Total Gate Charge and ON Resistance are in a trade-off relationship.
Generally, the smaller the chip size (surface area) of the MOSFET the smaller total charge but the ON resistance will increase.
In other words, there is a conflicting relationship between switching loss and power loss during operation.
Dynamic Input Characteristics
The figure shows an example of the dynamic input characteristics (Qg-VGS).
In the figure, the drain side supply voltage (VDD) and drain current (ID) are fixed, and the minimum amount of charge necessary for ID=30A (VDD=300V) current to flow is 60nC. At this time, the Gate-Source voltage (VGS) is 6.5V.
Actually, in a state where MOSFET switching can be completely turned ON, the ON resistance which is in a reciprocal relationship is adjusted and the gate voltage (VGS) set.
In this case, the total gate charge (Qg) can be read from the graph of the set voltage (e.g. 85nC at VGS=10V, 130nC at VGS=15V).
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Transistors
Basic
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Basics of Transistors
- Transistor Fundamentals: Structure, Types, and Operating Principles
- Bipolar Junction Transistor (BJT) Basics: Operation and Applications (NPN & PNP)
- NPN Transistor: Low-Side Switch Fundamentals
- PNP Transistor: High-Side Switch Fundamentals
- What is a Digital Transistor?
- Digital Transistor Selection
- ON Resistance
- Total Gate Charge
- How to select＜Selecting Transistors to Ensure Safe Operation＞
- Junction Temperature ＜Calculating Transistor Chip Temperature＞
- What is a Load Switch?
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Basics of MOSFETs
- What are MOSFETs? – MOSFET Parasitic Capacitance and Its Temperature Characteristic
- What are MOSFETs? – MOSFET Switching Characteristics and Temperature Characteristics
- What are MOSFETs? – MOSFET Threshold Values, ID-VGS Characteristics, and Temperature Characteristics
- What are MOSFETs? – Super-junction MOSFET
- What are MOSFETs? – Types and Features of High Voltage Super-Junction MOSFET
- What are MOSFETs? – Fast trr SJ-MOSFET：PrestoMOS™
- MOSFET Thermal Resistance and Power Dissipation: Packages Capable of Back-Surface Heat Dissipation
- Introduction
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Confirming the Suitability of a Transistor in Actual Operation – Introduction
- Confirmation of the Chip Temperature
- Confirmation of Suitability in Actual Operation and Preparations
- Confirmation that Absolute Maximum Ratings are Satisfied
- Confirmation that Operation is within the SOA (Safe Operating Area)
- Confirmation that Operation is within the SOA Derated at the Actual Operating Temperature
- Confirmation that Average Power Consumption is within the Rated Power
- Summary
- Summary
Evaluation
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The Importance of the Recovery Characteristics of Primary-side Switching Elements in LLC Converters －Introduction－
- Basic Configuration of an LLC Converter
- Features of LLC Converter Operation
- Basic Operation of LLC Converters
- Importance of MOSFET Recovery Characteristics for Off-Resonance of LLC Converters
- The Importance of the Recovery Characteristics of Primary-side Switching Elements in LLC Converters ーSummaryー
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The Importance of the Reverse Recovery Characteristics of Switching Elements in Inverter Circuits －Introduction－
- Types of Inverter Circuits and Energization Methods
- Basic Operation of 3-Phase Modulation Inverter Circuits
- Comparison of Losses in a PrestoMOS™ MOSFET and a Standard SJ MOSFET Using Double-Pulse Tests (Actual Measurement Results)
- Comparison of Efficiency of a PrestoMOS™ MOSFET and a Standard SJ MOSFET in a 3-Phase Modulation Inverter Circuit (Simulations)
- The Importance of the Reverse Recovery Characteristics of Switching Elements in Inverter Circuits －Summary－
- Mechanisms of MOSFET Destruction
- About Double-Pulse Tests
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Improving the Power Conversion Efficiency of Phase Shift Full Bridge Circuits – Introduction
- Basic Configuration of a PSFB Circuit
- Basic Operation of PSFB Circuits
- Guidelines Relating to Operation of Switching Elements Under Light Loading
- Guidelines Relating to Operation of Switching Elements Under Heavy Loading
- Evaluation of Efficiency
- Improving the Power Conversion Efficiency of Phase Shift Full Bridge Circuit – Summary –