Experiment 11 - The Heat Generation of the Voltage Regulator LM2940

So what about the heat generation or power dissipation of a Low-Drop-Out voltage regulator...?

The voltage regulator LM2940 has an internal construction comparable with the voltage regulator 78xx. Therefore the power dissipation of the LM2940 is described approximately by the formula...

P_D = (U_in - U_out) × I_out

     = (9.0 V - 5.0 V) × 0.50A = 2.00 Watt.

Circuit diagram heat generation voltage regulator LM2940.

Circuit heat generation voltage regulator LM2940. (Enlarge)

While pressing the push-button switch S1 the load resistor R1 and the voltage regulator become, as in the Experiment 7, very hot!

The advantage of a Low-Drop-Out voltage regulator does not lie in the overall power dissipation. Only at an input voltage V_in = 5,5 V is the power dissipation minimal...

P_Dmin = (V_DO) × I_out

           = 0.5 V × I_out

This is now much less than that of a 78xx...

With applications in closed, narrow environments this can be the decisive argument for a Low-Drop-Out voltage regulator...

Now you continue with adjustable voltage regulators...