AN-944 Datasheet, PDF (1/5 Pages) International Rectifier – Application Note

Application Note AN-944
Use Gate Charge to Design the Gate Drive Circuit for Power
MOSFETs and IGBTs
Table of Contents
Page
1. Input behavior of a MOS-gated transistor ......................................................... 1
2. Test Circuit........................................................................................................ 1
3. The Gate Charge Curve.................................................................................... 3
4. Beware When Comparing Different Products ................................................... 4
Designers unfamiliar with MOSFET or IGBT input characteristics begin drive circuit design by
determining component values based on the gate-to-source, or input, capacitance listed on the
data sheet. RC values based on the gate-to-source capacitance normally lead to a gate drive that
is hopelessly inadequate.
Although the gate-to-source capacitance is an important value, the gate-to-drain capacitance is
actually more significant—and more difficult to deal with—because it is a non-linear capacitance
affected as a function of voltage; the gate-to-source capacitance is also affected as a voltage
function, but to a much lesser extent.