High Amplitude Arbitrary/Function Generator Simplifies Measurement in Automotive, Semiconductor, Scientific and Industrial Applications Application Note
Figure 4. Setup for measuring switching time of a power MOSFET.
Figure 5. The AFG3011 shows the amplitude directly on the display.
Time related parameters of interest are turn-on and turn-off delay, as well as rise and fall time. To measure these parame- ters, the MOSFET's gate is stimulated with a narrow pulse from the signal generator input. The gate and drain voltages are measured with an oscilloscope (see Figure 4).
Using an arbitrary/function generator with integrated high amplitude output stage instead of an external amplifier gives the user direct visibility of the effective signal amplitude at the MOSFET's input circuit without the need to measure it with an oscilloscope.
The turn-on delay can now be determined conveniently via cursor measurements on the trace displayed on the oscillo- scope screen. Turn-on delay is the time it takes from the moment the gate-to-source voltage reaches 10% of its final value until the drain-to-source voltage declines to 90% of its initial value. Similarly, turn-off delay is the time taken from the moment the gate-to-source voltage declines to 90% of its previous level until the drain-to-source voltage has risen to 10% of the supply voltage. For the measurement of the drain signal's rise and fall times, modern oscilloscopes offer convenient automated measurements.
Figure 6. Measuring switching time of a power MOSFET.