AN4030

Gate to cathode capacitor, impact on dV/dt immunity

Doc ID 022635 Rev 1

5/15

Figure 4.

SCR simplified silicon structure and spurious capacitive current

A better solution could be found if a capacitor is used instead of a resistor. A high-voltage

typically) is applied across this capacitor.

Figure 5 shows the typical relative dV/dt increase versus gate-cathode capacitance for an

ten times with a 100 nF gate to cathode capacitor.

It should be noted that a gate to cathode resistor is still used in parallel with the gate to

cathode capacitor to discharge it after gate current removal.

improve dV/dt immunity a lot. Indeed, these devices already feature a very low internal gate

to cathode resistor. So adding any external component is not very efficient to shunt the

spurious capacitive current.

N1

P2

N2

P1

Cathode (K)

Gate (G)

Anode (A)

C N1/P1

C P1/N2

C N2/P2

R

GK