Overview

As shown in the diagram on the right, this product has a Si MOSFET and SiC JFET internally cascode-connected in a single package, allowing it to be designed in the same way as conventional silicon MOSFETs.

Another advantage is that it does not require a negative power supply and can be driven with existing gate circuits and general-purpose gate drivers. The advantages of cascode JFETs are explained below.

Advantage 1: No negative power supply required

The recommended operating voltage of VGS for cascode JFETs is very user friendly.
The gate voltage threshold is 4.8V at 25°C. Therefore, a negative power supply is not required because the gate voltage threshold is high.
As shown in the figure below, the recommended operating VGS of a cascode JFET is 0 to 12V, the same as that of a general silicon MOSFET.

Ordinary SiC MOSFETs can have a low gate voltage threshold, requiring a negative power supply to completely turn them off.

Advantage 2: Can be driven by existing gate circuits

Next, the absolute maximum rating of VGS for cascode JFETs is ± 20V, the same as for general silicon MOSFETs.
This allows it to be driven by existing gate circuits and general-purpose gate drivers.

Advantage 3: Low on-resistance

Because this cascode JFET uses a SiC JFET, it does not have the channel resistance of other companies' typical SiC MOSFETs, making it possible to reduce the total on-resistance to about 1/4 to 1/2, thereby achieving low on-resistance (see the schematic cross-section diagram below).

However, although the cascode connection increases the ON resistance of the Si MOSFET, because it is a low-voltage Si MOSFET, this is only about 1/10 of the channel resistance, so the effect can be ignored.

Advantage 4: Low VF

Next, the characteristics of the body diode, which are related to switching characteristics,
First of all, the body diode of a typical SiC​ ​MOSFET uses SiC, so VF is high, at 3.5 V or higher. In addition, the Qrr characteristics are not very good, and the value increases very quickly depending on the temperature.

However, in a cascode JFET, the body diode is made of silicon.
Current flows from source to drain through the body diode of the Si MOSFET and through the JFET, with the SiC​ ​JFET itself acting as just a resistor.
The body diode characteristics are those of a low-voltage MOSFET, with a low VF of 1.5V.

Cascode JFET product page

Please check the ONSEMI website for the lineup of cascode JFETs that offer these advantages.

Inquiry / Quotation

If you have any questions about this product or would like a quote, please contact us using the form below.