Temperature Effects

TEMPERATURE EFFECTS

The characteristics of MOSFET varies with change in temperature as shown in Fig.5.27.

At V_GS values from 4V to 6 V, temperature coefficient of i_D is zero. At higher values, i_D exhibits a negative temperature coefficient.

This indicates that thermal runaway will not occur in MOSFET even if operated beyond zero temperature coefficient. In low current region (< zero temperature coefficient), the temperature coefficient of i_D is positive and thermal runaway occurs.

COMPARISON OF POWER MOSFET WITH POWER BJT

1. MOSFET provides a very good isolation between the gate and other two terminals compared to BJT

2. MOSFET can handle more power compared to BJT

3. MOSFET has very low power less and a high speed

4. Voltage signals can easily operate a MOSFET, hence it is used in many digital circuits for switching applications ex: motor control circuits.

5. Power MOSFET do not suffer from second breakdown compared to BJT.

6. Power MOSFET do not require large de large- drive current as that in power BJTs.

7. Higher speed of operation than power BJT.

Applications

1. Low stepping motor

2. Low voltage/high-voltage brushless DC motor

3. Switching power supply