Fairchild AN-7502 manual Ro = Rd

Page 8

Application Note 7502

Case 3 :Common-Source Gate Drive, Figure B-3

10V

VDD

FIGURE B-3. COMMON-SOURCE GATE-DRIVE CIRCUIT

Turn-On

RO = RD

(drain-to-ground capacitance of driving device adds to CGS of driven MOSFET.)

Turn Off

RO = rDS(ON) of driving MOSFET when

RD is very much greater than RDS(ON)

Application Note 7502 Rev. A1

Image 8

Contents Device Models Gate Drive Constant Voltage or Constant CurrentApplication Note Equivalent CircuitSix States State 1 MOS Off, Jfet OffNew Device Characterization State 2 MOS ActIve, Jfet ActIveState 3 MOS Active, Jfet Saturated State 4 MOS Saturated, Jfet Saturated Turn-OffStep-Voltage Gate Drive RatesUsing the Characterization Curve, Figure State 2 & 6 MOS Active, Jfet ActiveState 4 MOS Saturated, Jfet Saturated State 5 MOS Active, Jfet SaturatedCharacterization-Curve Limits ConclusionsAppendix a Analysis for Resistive Step Voltage Inputs Step Voltage Gate DriveTurn-Off State 6 Mos Active, Jfet ActiveCase 1 Typical Pulse-Generator Drive, Figure B-1 Turn-On and Turn-OffRO = RD Crossvolt