Pulsed Characterization of Power Semiconductors Using Electronic Loads
Application Notes
Electronic Load Improves Power Semiconductor Measurements
An electronic load eliminates the selfheating problems associated with measuring the on-state voltage drop and transconductance (or current gain) of power semiconductors.
On-state voltage drop and transconductance (or current gain) of power FETs, BJTs, and IGBTs are temperature dependent, but are typically specified at 25 °C. However, it is difficult to obtain an accurate measurement of these parameters because the manufacturer’s test conditions can cause the device to dissipate significant peak power, which will raise the device temperature above 25 °C. Sometimes the amount of peak power exceeds the device’s static power rating by nearly 6:1! For example, an IRF540 FET is rated at 150 W continuous, but the transconductance gfs is specified at a test condition of 17 A and 50 V, or 850 W. If the device is subjected to this test condition too long it will self-heat, and its junction temperature will no longer be 25 °C, so measurements will be inaccurate