What are the capacitance characteristics of MOSFET.

Ciss, Crss and Coss are all important factors that influence switching characteristic of MOSFET.

  • Ciss: input capacitance (Ciss=Cgd+Cgs)
    ⇒Sum of gate-drain and gate-source capacitance. It influences delay time. The greater Ciss, the longer the delay time.
  • Crss: Reverse transfer capacitance (Crss=Cgd)
    ⇒Gate-drain capacitance. The greater Crss, the worse the drain current rising characteristics, which is disadvantageous for MOSFETs’ loss. Low capacitance is needed for high-speed driving.
  • Coss: Output capacitance (Coss=Cgd+Cds)
    ⇒Sum of gate-drain and drain-source capacitance. It influences turn-off characteristic and loss with light load. The greater Coss, the lower the turn-off dv/dt, which is advantageous for noise. But loss with light load increases.