Engineering Reference

MOSFET Datasheet Parameters Reference

Quick-reference MOSFET parameters including VGS(th), RDS(on), VDS, drain current, gate charge, capacitances, SOA, body-diode recovery, avalanche, and thermal ratings.

Reading Time: 14 min
Format: Datasheet lookup
Updated: September 24, 2026

Quick MOSFET Parameter Lookup

Quick MOSFET parameter lookup
Need to check	Datasheet parameter	Condition to retain
Maximum drain-source voltage	VDS	Absolute maximum plus transient and derating analysis
Gate voltage where specified conduction begins	VGS(th)	Threshold test current and temperature; not full enhancement
Low-loss on-state resistance	RDS(on)	Specified VGS, ID, TJ and guaranteed limit
Continuous or pulsed drain current	ID / IDM	Case or ambient temperature, package, pulse and thermal conditions
Safe voltage-current combinations	SOA	VDS, ID, pulse duration and temperature together
Gate-driver charge requirement	Qg / Qgd	Specified VDS, ID and gate-voltage excursion
Small-signal capacitances	Ciss / Coss / Crss	Specified VDS, VGS and frequency; voltage dependence matters
Body-diode recovery	Qrr / trr	Forward current, di/dt, temperature and commutation conditions
Avalanche capability	EAS / EAR / IAS	The exact single-pulse or repetitive test circuit and starting temperature
Thermal path	RθJA / RθJC / ZθJC	Board, case, mounting, airflow, pulse duration and interface conditions

Core Datasheet Parameter Table

Manufacturer symbols and test methods can differ. Read each value together with its table footnotes, curves and measurement circuit.

MOSFET datasheet parameter reference
Symbol	Parameter	Required condition	Engineering use	Common mistake
VDS	Drain-source voltage rating	Absolute maximum at stated temperature	Supply tolerance, overshoot and ringing	Combining VDS(max) with ID(max)
VGS(max)	Maximum gate-source voltage	Absolute positive and negative limit	Gate protection and driver clamp	Treating it as recommended drive
VGS(th)	Threshold voltage	Small specified ID, VDS and temperature	Turn-on onset and variation	Treating it as fully-on voltage
ID / IDM	Continuous / pulsed drain current	TC or TA, pulse width, duty cycle and thermal limits	Current capability	Using the headline current on any PCB
RDS(on)	On-state drain-source resistance	Specified VGS, ID and TJ	Conduction loss and sharing	Treating the 25°C typical value as constant
Qg	Total gate charge	Specified VDS, ID and VGS excursion	Driver energy and average current	Treating it as condition-independent
Qgs / Qgd	Gate-source / gate-drain charge	Gate-charge test operating point	Pre-plateau and Miller transition	Equating Qg with one fixed capacitor
Ciss	Input capacitance, commonly Cgs + Cgd	Specified VDS, VGS and frequency	Small-signal input behavior	Using it alone for exact switching time
Coss	Output capacitance, commonly Cds + Cgd	Specified bias and frequency	Switch-node energy and transition	Ignoring strong voltage nonlinearity
Crss	Reverse-transfer capacitance, commonly Cgd	Specified bias and frequency	Miller coupling and dv/dt	Assuming one value over the full VDS swing
td(on), tr, td(off), tf	Switching-time terms	Datasheet gate resistance, driver, load and voltage	First-order transition estimates	Transferring times to a different test circuit unchanged
VSD / VF	Body-diode forward voltage	Specified diode current, VGS and temperature	Dead-time loss and reverse conduction	Treating body-diode VF as fixed or Schottky-like
Qrr / trr	Reverse-recovery charge / time	IF, di/dt, temperature and commutation	Bridge loss, EMI and dead time	Comparing values from unlike tests
EAS / EAR / IAS	Avalanche energy / current ratings	Manufacturer avalanche test conditions	Inductive transient robustness	Assuming unlimited repetitive avalanche
PD	Power dissipation	Specified case or ambient temperature and thermal path	Thermal ceiling	Using it independently of cooling
TJ / TJ(max)	Junction temperature / limit	Operating and absolute maximum tables	Reliability and thermal margin	Confusing ambient with junction temperature
RθJA / RθJC / RθJB	Steady-state thermal resistances	Specified board, case, mounting and environment	Thermal-path estimate	Treating RθJA as a package-only constant
ZθJC	Transient junction-to-case thermal impedance	Pulse duration and duty-cycle curves	Short-pulse temperature rise	Using steady-state resistance for every pulse

Gate Threshold, Drive and On Resistance

VGS(th) is not fully-on voltage

Threshold is measured at a small specified drain current. It cannot establish that a GPIO voltage produces acceptably low RDS(on).

Logic-level needs a guaranteed RDS(on)

A logic-level label is not enough. Look for a guaranteed resistance at the actual 4.5 V, 2.5 V, 1.8 V or other gate drive used by the circuit.

RDS(on) is condition-dependent

Retain VGS, ID, TJ, typical/maximum status and production spread. For common silicon power MOSFETs, resistance usually rises with junction temperature; use the product curve or guaranteed limits.

VGS(max) protects the oxide

An absolute gate limit such as a positive/negative maximum is not a drive recommendation. Account for ringing, negative transients and ESD sensitivity.

Voltage, Current and SOA Boundaries

VDS needs transient margin

Supply tolerance, switching overshoot, ringing and inductive events all contribute. No single derating percentage fits every topology or reliability target.

ID is thermally conditioned

A headline current may assume a specified case temperature or strong cooling. Package leads, bond wires, board copper, thermal resistance, dissipation and SOA can set lower limits.

Absolute maxima cannot be multiplied

A 100 V, 50 A device is not thereby rated for 5000 W. VDS(max), ID(max) and PD(max) describe separate boundaries under their own conditions.

SOA governs combinations

Read the VDS-ID-time-temperature curves, especially for linear mode. Some switching-optimized MOSFETs have restricted linear SOA even below a headline PD value.

Gate Charge, Miller Region and Capacitance

Qg is a charge curve result

Total gate charge depends on the datasheet VDS, ID and VGS excursion. Qgd describes the Miller-region charge associated with drain-voltage transition.

Average is not peak current

Igate,avg ≈ Qg × fsw estimates average delivered charge. Peak current depends on desired transition time, gate resistance, driver impedance and Miller plateau.

Capacitances are nonlinear

Common definitions are Ciss = Cgs + Cgd, Coss = Cds + Cgd, and Crss = Cgd. They are small-signal quantities and vary with bias, especially VDS.

Charge and capacitance are not interchangeable

For switching energy, charge and energy curves can be more useful than one headline capacitance. Ciss alone is not a fixed physical gate capacitor.

Switching, Body Diode and Avalanche

Switching-loss estimate

Psw ≈ 0.5 × VDS × ID × (tr + tf) × fsw is only a first-order overlap estimate. Coss/Qoss, diode recovery, topology, parasitics, ringing, dead time and drive behavior add loss.

Body-diode parameters

VSD or VF depends on current and temperature. Qrr and trr depend on current, di/dt, temperature and commutation; the intrinsic diode must not be assumed equivalent to a discrete Schottky diode.

Avalanche ratings are conditional

EAS, EAR and IAS belong to a defined test circuit, current, inductance and starting junction temperature. An avalanche rating does not permit unlimited repetitive spikes.

N-channel and P-channel context

Gate polarity and common high-/low-side uses differ. N-channel devices often offer lower resistance at comparable technology, but neither channel type is universally better. Most power switches are enhancement-mode, not all MOSFETs.

Thermal Parameter Reference

Steady-state estimate

TJ ≈ TA + P × RθJA is valid only when the supplied effective RθJA represents the actual board, copper, airflow, mounting and package environment.

Use the correct thermal path

RθJC applies junction-to-case; RθJB applies junction-to-board; RθJA describes a complete test environment. They cannot be substituted without matching the physical heat path.

Short pulses need Zθ

Transient thermal impedance curves account for pulse duration and repetition. Applying steady-state RθJC or RθJA to every short event can over- or underestimate junction rise.

Package depth belongs elsewhere

This page interprets thermal symbols needed with MOSFET ratings. Full TO-220, DPAK, DFN, SO-8 and mounting comparisons remain in REF-MOS-002.

Worked Reference Examples

Conduction loss

5² × 0.020 Ω = 0.50 W. With an assumed hot resistance of 30 mΩ, 5² × 0.030 Ω = 0.75 W. Both resistance values are explicit example assumptions.

Gate charge and drive power

40 nC × 100 kHz = 4 mA average and 40 nC × 10 V × 100 kHz = 40 mW. Four milliamperes average does not define peak driver current.

Simplified switching loss

0.5 × 24 V × 5 A × (20 + 20) ns × 100 kHz = 0.24 W. This omits nonlinear capacitance, recovery and parasitic effects.

Steady-state temperature

40°C + 1 W × 50°C/W = 90°C. The result is only as valid as the assumed effective RθJA for the actual board.

Datasheet Lookup Workflow

1Determine required VDS and transient conditions.
2Identify the actual gate-drive voltage and limits.
3Verify guaranteed RDS(on) at that VGS.
4Apply RDS(on) temperature behavior and production limit.
5Check ID under the real thermal and package conditions.
6Check SOA at the required VDS, ID, time and temperature.
7Estimate conduction loss with RMS current and duty interval.
8Check Qg, Qgd and driver peak-current capability.
9Estimate switching loss where the topology permits.
10Review Coss/Qoss and switching-node behavior.
11Check body-diode VF, Qrr and dead-time requirements.
12Build the real thermal path and verify TJ.
13Check avalanche and transient requirements if applicable.
14Confirm curves, footnotes and test circuits in the manufacturer datasheet.

Common Interpretation Mistakes

Treating VGS(th) as full-on voltage.
Choosing logic-level suitability from threshold alone.
Treating RDS(on) as constant.
Using only 25°C typical RDS(on).
Treating headline ID as universal safe current.
Combining VDS(max), ID(max) and PD(max).
Ignoring SOA or linear-mode SOA.
Treating VGS(max) as recommended drive.
Treating Qg as fixed under all conditions.
Confusing average and peak gate current.
Treating Ciss as a fixed gate capacitor.
Ignoring Coss and Crss nonlinearity.
Ignoring body-diode Qrr.
Assuming body-diode VF is fixed.
Assuming avalanche rating permits unlimited events.
Ignoring package and PCB thermal conditions.
Using RθJA as a universal constant.
Selecting a MOSFET only by RDS(on).

Support reference

FAQ

What does VGS(th) mean?

VGS(th) is the gate-source voltage at which the datasheet observes a specified small drain current under stated test conditions. It marks threshold-region conduction, not low-resistance full enhancement.

Is VGS(th) the voltage required to fully turn on a MOSFET?

No. Verify RDS(on) at the actual gate-drive voltage, current and temperature. A gate voltage above maximum threshold may still be insufficient for low-loss operation.

How do I know whether a MOSFET works with 3.3 V gate drive?

Look for a guaranteed RDS(on) specification at 3.3 V or a suitably lower VGS, then check its temperature behavior, current, SOA and driver conditions. Do not decide from VGS(th) alone.

What is RDS(on)?

RDS(on) is on-state drain-source resistance measured at stated VGS, ID and temperature. It varies across production and usually rises as a silicon power MOSFET heats.

Can I use the maximum drain-current rating continuously?

Not automatically. ID depends on thermal conditions, package and interconnect limits, SOA, power dissipation, board copper and junction temperature.

What is MOSFET SOA?

Safe Operating Area defines allowed combinations of VDS, ID, pulse duration and temperature. It is especially important for linear operation and transient stress.

What is gate charge?

Gate charge describes charge moved through the gate over a stated switching test. Qg and Qgd support driver-energy and transition analysis but vary with the test operating point.

Is gate charge the same as gate capacitance?

No. Capacitances are bias-dependent small-signal quantities; charge integrates nonlinear device behavior over a voltage transition. They are related but not freely interchangeable.

What are Ciss, Coss and Crss?

They are common small-signal input, output and reverse-transfer capacitance definitions. Their values, especially Coss and Crss, change with drain voltage.

What does Qrr mean?

Qrr is body-diode reverse-recovery charge under stated current, di/dt and temperature conditions. It can affect hard-switching loss, ringing and EMI.

What is avalanche energy?

Avalanche energy is a controlled-test rating such as EAS or EAR. It does not imply unlimited or condition-free absorption of inductive transients.

Is VGS(max) the recommended gate-drive voltage?

No. VGS(max) protects the gate oxide as an absolute limit. Recommended drive follows the RDS(on), charge and application requirements with adequate margin.

What thermal parameters should I check?

Check TJ(max), the relevant Rθ or transient Zθ path, dissipation, PCB or heatsink conditions, interface resistance, ambient or case temperature, and pulse duty cycle.

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