Linear Regulators

LINEAR REGULATORS   

·           All electronic circuits need a dc power supply for their operation. To obtain this dc voltage from 230 V ac mains supply, we need to use rectifier.

·           Therefore the filters are used to obtain a ―steady‖ dc voltage from the pulsating one.

·           The filtered dc voltage is then applied to a regulator which will try to keep the dc output voltage constant in the event of voltage fluctuations or load variation.

·           We know the combination of rectifier & filter can produce a dc voltage. But the problem with this type of dc power supply is that its output voltage will not remain constant in the event of fluctuations in an ac input or changes in the load current(IL).

·           The output of unregulated power supply is connected at the input of voltage regulator circuit.

·           The voltage regulator is a specially designed circuit to keep the output voltage constant.

·           It does not remain exactly constant. It changes slightly due to changes in certain parameters.

Factors affecting the output voltage:

i)          IL (Load Current)

ii)       VIN (Input Voltage)

iii)     T (Temperature)

IC Voltage Regulators:

They are basically series regulators with all the basic blocks present inside the IC. Therefore it is easier to use IC voltage regulator instead of discrete voltage regulators.

Important features of IC Regulators:

1.        Programmable output

2.        Facility to boost the voltage/current

3.        Internally provided short circuit current limiting

4.        Thermal shutdown

5.        Floating operation to facilitate higher voltage output