Power mosfet characteristics

It's all about power mosfet.

1. POWER MOSFET CHARACTERISTICS Julius Edgar Lilienfeld Robert W. Bower PATENTED BY - INVENTED BY - MOSFET - Source Internet

2. 1440 V/400 A 10 kHz 1000 V/50 A 100 kHz 1200 V/300 A 100 kHz 1200 V/500 A 50 kHz TRANSISTOR FAMILY

3. G D S METAL-OXIDE-SEMICONDUCTOR FIELD-EFFECT TRANSISTOR It is combination of field-effect concept and MOS technology .

4. HOW MOSFET DIFFER FROM BJT ?

5. WHY WE NEED POWER MOSFET ? V DD V GS Large on-load resistance On increasing V GS more current flows This leads to high power dissipation in n -channel and breakdown occurs. In n -channel planar MOSFET

6. POWER MOSFET(PMOSFET) It consists of DIFFUSED METAL-OXIDE-SEMICONDUCTOR V GS GATE SOURCE SOURCE METAL SiO 2 V DD n + n+ n+ n+ P n- n- n+ n+ substrate DRAIN P On-resistance can be made low if short length is used for n -channel . npn BJT

7. PMOSFET CHARACTERISTICS V GS V DS I D R R D V G V DD Transfer characteristics Output characteristics Switching characteristics

8. TRANFER CHARACTERISTICS Variation of drain current I D as a function of gate source voltage V GS 2 4 6 8 10 12 I D (A) V GS(V) V GST Threshold voltage(V GST ) - The minimum positive voltage between gate and source to induce n -channel.

9. OUTPUT CHARACTERISTICS Active Ohmic i D V DS A B Cut-off When V GS <V GST Drain source breakdown voltage Drain current (A) Drain-source voltage Low value of V DS curve is linear i.e. constant on-resistance RD. For given V GS on increasing V GS curve is flat i.e. drain current is constant. V GS is large, MOSFET turns on small V DSON . MOSFET acting as closed switch & driven into ohmic region (Saturation region in BJT). When device on PMOSFET curve traverse from cut-off to active region then to ohmic region & when turns off, takes backward journey from ohmic to cut-off region.

10. SWITCHING CHARACTERISTICS V G V1 t1 t V GS V1 V GSP V GST t dn t r t df t f t d t on I D t t T dn is turn on delay time during which i /p capacitance charges to threshold voltage(V GST ). Rise time( t r ) – gate voltage rises to V GSP (voltage sufficient to drive the MOSFET) & drain current rises from zero to full-on current(I D ). Total turn-on time (t on ) = t dn + t r . t r can be reduced using low-impedance gate –drive source. Turn-off process starts at time t1. Turn-off delay time( t df ) – i /p capacitance discharges from overdrive gate voltage V1 to V GSP . Fall time( t f ) – i /p capacitance discharges from V GSP to V GST & I D falls to zero. So, when V GS ≤V GST PMOSFET is turned-off.

11. QUERY TIME

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