What exactly is an LM7805 Voltage Regulator?

[Jotrinelectronic]

The LM7805 is a nifty device designed to output a stable +5 volts.

 

Here's a handy trick to recall the output voltage for the LM78XX series of voltage regulators: focus on the last two digits of the number. In the case of the LM7805, the "05" signals a 5-volt output. The prefix "78" is just a labeling convention used by chip manufacturers to indicate a series of regulators generating positive voltage. Conversely, the LM79XX series is responsible for producing negative voltage. To sum it up:

• LM78XX: Positive voltage regulators with "XX" denoting the output voltage.
• LM79XX: Negative voltage regulators with "XX" representing the output voltage.

The LM7805, typical of most regulators, is a three-pin integrated circuit (IC). Breakdown:

1. Pin 1 (Input): This is where the DC voltage comes in, ready to be regulated down to a solid 5 volts.
2. Pin 2 (Ground): Grounding happens here, providing stability to the regulator.
3. Pin 3 (Output): The output is a steady 5 volts of direct current.

However, a word of caution: while the LM7805 can handle input voltages up to 36 volts, it's advisable to cap it at 2-3 volts above the regulated output. For a 5-volt regulator, keep the input voltage under 8 volts. Why? Well, the excess voltage transforms into heat. The wider the gap between input and output, the more heat is generated. Excessive heat, without a heat sink to dissipate it, can lead to the regulator overheating and malfunctioning. So, you have two choices: limit the input voltage or introduce a heat sink into your circuit to manage the heat.

For further insights into integrating a regulator into your circuit, explore: 7805 Voltage Regulator IC