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f-alpha.net » Electronics » Integrated Circuits » Voltage Regulator » Let's go... » Experiment 11 - LDO Voltage Regulator II

Experiment 11 - The Heat Generation of the Voltage Regulator LM2940

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...

PD = (Uin - Uout) × Iout

     = (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 Vin = 5,5 V is the power dissipation minimal...

PDmin = (VDO) × Iout

           = 0.5 V × Iout

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...

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