why is a heat sink used for the MOSFET in some cases? What does it do?

Question

building a circuit with a small motor and a light.

Answer 1

The heatsink is used to help the chip dissipate heat which is the result of power loss through resistive heating of the silicon while conducting a lot of current (I²R losses). The heat sink fins provide surface area with which the chip can exchange heat with the surrounding air. The quicker you conduct the heat away from the transistor, the higher current you can put through it without melting it.

Answer 2

Heat sinks are used to help dissipate heat of active devices to prevent them from destroying themselves.

Mosfets have a positive temperature coefficient of resistivity ie: as they get hotter, they get lossier, hence become more resistive and they start to restrict more current.

Maximum junction temperature on active devices is typically 150 degrees C. Never allow the junction to go past a derating of 130 deg. C.

You have to know the Junction to ambient thermal resistance and calculate (knowing the voltage and current on the device) if you need a heat sink or not.

Mosfet switching losses (turning on and off) is where the most loss occurs.

If you're using it for a motor -- PICK YOUR SNUBBER CAREFULLY or you'll damage the device for sure.

Also, check into using a gate resistor (typically around 10 ohms depending upon the mosfet) to slow the turn on and off a little bit, if it's too fast, the inductive kick from the motor can make HUGE spikes on turn on and turn off which again can destroy the mosfet or other equipment.

Answer 3

The heatsink removes the heat dissapated from the transistor. You are probably using it as a switch which will not cause too much heat dissipation, however, MOSFETS channel resistance increases with temperature, causing the device to heat up to the point of destruction. As the resistance increases, more power is lost in the source / drain channel.

Answer 4

The enemy of all electronics is heat. U must dissipate the heat or it will destroy the MOSFET . If u design the ckt right u can reduce the heating some . The secrete is to turn it full on and full off . That will dissipate less heat but does not work on a linear amp.

Answer 5

Heat sinks keep mosfets (and other chips) cool.

Some don't generate as much heat as others and don't require a heat sink - usually it will come with one if it is necessary, but you should probably always doublecheck the manufacturers specs/recommendations depending on what the application will be.

Answer 6

Helps to dissipate the heat from the device. If the part over heats (volts x amps = watts, watts = heat) it fails.

Open up your PC and look at the big honking heat sink on your Intel CPU.

Answer 7

Any transistor must have its junctions held below a certain temperature to prevent failure. When power gets excessive, this is accomplished by mounting the transistor on a device that can carry heat away and keep it cool.

Answer 8

a heat sink is made of a material that is almost always cool to the touch by adind a fan on top of it it will stay cool and cool down your proseser so it dosnet over heat