AN957 Datasheet, PDF(7/13 Page) List of Unclassifed Manufacturers

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AN957 Datasheet, PDF (7/13 Pages) List of Unclassifed Manufacturers – Measuring HEXFETCharacteristics

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Index

AN-957 (v.Int)

11. Measurement Of HEXFET Power Mosfet Characteristics

Without A Curve Tracer

BVDSS

250 ÂµA

HEXFET Power MOSFET parameters can be measured using

standard laboratory equipment. Test circuits and procedures for

doing this are described in the following sections, with the IRF630

DVM

used as an example. the test arrangement should be varied

appropriately for other devices.

BVDSS, Drain-Source Breakdown Voltage

Figure 13. Test circuit for BVDSS

The test circuit is shown in Figure 13. The current source will typically consist of a power supply with an output voltage

capability of about 3 time BVDSS in series with a current defining resistor of the appropriate value.

When testing high voltage HEXFET Power MOSFETs it may not be practical or safe to use a supply of 3 times BVDSS. In such

cases, another type of constant current source may be used.

VGS(th), Threshold Voltage

The test circuit is shown in Figure 14. The 1 kohm gate resistor is required to suppress potentially destructive oscillations at the

gate. the current source may be derived from a voltage source equal to the gate voltage rating of the HEXFET Power MOSFET

and a series resistor.

VDS(on), On-Resistance

The test circuit is shown in Figure 15. The pulse

width should be 300 microsec at a duty cycle of less

than 2%.

The value quoted is at a junction temperature of 25ÂºC.

RDS(on) is calculated by dividing VDS(on) by ID. Connect

the ground of the gate supply as close to the source

lead as possible.

VGS(th)

DVM

1Kâ¦ G

250 ÂµA

gfs, Transconductance

Figure 14. Test circuit for gate threshold voltage

Connect a 50V power supply

between the device drain and

source, as shown in Figure 16. Use

a current probe to measure ID.

A signal generator operating at low

duty cycle to prevent heating of the

BVDSS

device, is used to obtain 80

microsec pulses of the required

voltage (VGS) to obtain the

following currents:

OSCILLOSCOPE

or DVM

PULSE COMMAND

10V

0.015 x ID , 0.05 x ID , 0.15 x ID , 0.5

x ID , and 1.5 x ID where ID is the

rated value at TC = 25ÂºC. Plot a

graph of VGS versus ID.

The transconductance is equal to the slope of the graph at the Fapigpurorper1ia5t.eTveasltuceirocfuditrafoinr cdurarrinenotn. -state voltage

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