IRFP9240 Output Curve Characterization

Application

This circuit characterizes the IRFP9240 P-channel power MOSFET by sweeping source-drain voltage while stepping source-gate voltage. It is useful when comparing the threshold region, low-voltage triode behavior, and high-current output characteristics before choosing a high-side gate-drive level or load condition.

Design Context

VSD is the swept source supply and drives the MOSFET source positive relative to the grounded drain return. VSG is a second DC source from source to gate and is stepped as the secondary sweep, creating a family of drain-current curves from one schematic. The MOSFET symbol is vertically mirrored so the P-channel source sits on the high side and the drain current path returns downward through the Id current probe.

Expected Behavior

Drain current magnitude increases as VSG rises above the threshold region. At low VSD, the curves show the low-resistance triode region; as VSD increases, each curve bends toward the model output characteristic for that gate drive.

Key Values

• VSD sweep: 0 V to 12 V in 1 V steps.
• VSG sweep: 4 V to 10 V in 2 V steps, which corresponds to gate-source drive from -4 V to -10 V.
• Id: drain current measured in the lower drain branch.
• Drain return: common ground reference for the sweep source negative terminal.

Suggested Experiments

• Narrow the VSD sweep around 0 V to 2 V to inspect the triode-region knee.
• Adjust the VSG step range to compare near-threshold drive against stronger gate drive.
• Add a realistic high-side load after reviewing the raw output curves to see how the load line intersects the MOSFET behavior.

Featured Component

The IRFP9240 is the P-channel power MOSFET under test. Its gate-source voltage controls the drain-source channel current, so this output-curve demo focuses on how the device conducts for different high-side gate-drive levels.