QSPICE Schematic Capture “GaN Output Cap”

[mccunets]

For this week’s QSPICE schematic capture, we have one by our own Mike Engelhardt. QSPICE has introducing new FET device equations for GaN. This circuit shows how the output capacitance can be extracted.

V1 sets the Vds voltage and asserts a 1MHz AC voltage. The capacitance can then be plotted as I(V1)/(2pi1Meg).

SPICE device equations don’t usually encapsulate FET output capacitance which make simulating soft switching impossible. The new device equations in QSPICE solves this problem.

Please send any submissions to me at tim.mccune@qorvo.com (Schematic Capture Post #091)

GaNoutputCap.qsch (2.0 KB)

[bordodynov]

I am glad to see new models. Here is a more correct definition of the output capacity:

[KSKelvin]

In today’s update, .plot accepts definitions for the vertical plotting style:
07/21/2026 .plot statements accept LIN, LOG, and dB as a directive for that windows vertical plotting style.

LIN was added to .plot to force a linear y-axis, and .abscissa was used not only to set Vds as the x-axis, but also to display its label. In short, this schematic gets everything set up with dot command.

GaNoutputCap-LIN.qsch (2.2 KB)