Regulated Power Supply

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5V Simple Power Supply for Digital Circuits

Introduction

The +5 volt supply is useful for both analog and digital circuits. DTL, TTL, and CMOS ICs will all operate nicely from a +5 volt supply. In addition, the +5 volt supply is useful for circuits that use both analog and digital signals in various ways.

More importantly for our purposes, the +5 volt supply will be used as the primary reference for regulating all of the other power supplies that we will build. We can do this very easily if we use operational amplifiers as the controlling elements in the power supply circuits. We'll see how this works after completing the basic +5 volt supply.

Summary of circuit features

* Brief description of operation: Gives out well regulated +5V output, output current capability of 100 mA

* Circuit protection: Built-in overheating protection shuts down output when regulator IC gets too hot

* Circuit complexity: Very simple and easy to build

* Circuit performance: Very stable +5V output voltage, reliable operation

* Availability of components: Easy to get, uses only very common basic components

* Design testing: Based on datasheet example circuit, I have used this circuit succesfully as part of many electronics projects

* Applications: Part of electronics devices, small laboratory power supply

* Power supply voltage: Unreglated DC 8-18V power supply

* Power supply current: Needed output current + 5 mA

* Component costs: Few dollars for the electronics components + the input transformer cost

Circuit description

This circuit is a small +5V power supply, which is useful when experimenting with digital electronics, and easy to build. Small inexpensive wall tranformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily available, but usually their voltage regulation is very poor, which makes then not very usable for...