Temperature Control

Resistance of thermistor will drop once it get heated.
Voltage of +input higher than -input => Output => Saturate NPN => Run the fan
1000uF to smooth out the voltage source ripple and start-up for fan.

Do not exceed voltage rating of components and make sure NPN's current rating is capable for your fan.

Components:
12volts power supply
Op Amp (mono)
NPN transistor
Resistors
Thermistor
Fan
Capacitor 1000uF



A cooling solution for you after an Extreme Hot Peri Peri. =]