78L05 Voltage Regulator: Active Voice Revision

Pin Configuration

78L05 Regulator Features

• The 5V Positive Voltage Regulator provides a fixed output.
• It delivers an Output Current of up to $100\text{mA}$.
• The IC handles a Maximum Input Voltage of $30\text{V}$.
• Its Operating Current (IQ​) is $5\text{mA}$.
• The IC includes internal Thermal Overload and Short Circuit Current Limiting protection.
• We offer it in the TO-92 package.
• Note: Find complete technical details in the $\text{78L05}$ datasheet at the end of this page.

Where to Use the 78L05

Voltage regulators are very common in electronic circuits. They provide a constant output voltage despite a varied input voltage. The 78L05 IC is an iconic regulator IC. It finds application in most projects. The name $78\text{L}05$ has two meanings: “78” signifies a positive voltage regulator, and “05” means it outputs $\text{5V}$. Thus, our $7805$ delivers a $+\text{5V}$ output voltage.

This IC’s output current can reach $100\text{mA}$. However, the IC dissipates heavy heat. Therefore, we recommend a heat sink for projects consuming more current. For example, if you use a $12\text{V}$ input and draw $50\text{mA}$, the IC dissipates (12−5)×(50×10−3)=0.35W as heat.

The popular 7805 is another voltage regulator. It is physically bulkier but handles a high current rating of about $1\text{A}$. If you need a smaller package regulator with a lower current rating in a $\text{TO-92}$ package, this IC is the right choice.

How to Use the 78L05

The 78L05 is a three-terminal voltage regulator. The three terminals are Input, Output, and Ground, as the $\text{78L05}$ pinout diagram shows. You can use this IC easily and straightforwardly. Just connect the input pin to the unregulated input voltage and the ground pin to the system ground.

The circuit below uses the $\text{78L05}$ to regulate a $12\text{V}$ input voltage down to $\text{5V}$. You use the $\text{5V}$ to power any small loads, such as an $\text{LED}$, that draw less than $100\text{mA}$. This is because the IC can only supply a maximum current of $100\text{mA}$.

Also, note that capacitors $\text{C}1$ and $\text{C}2$ sit at both the Input and Output terminals. These capacitors filter any noise coupled with the Input voltage. You don’t need to use the exact capacitor value, but $10\mu \text{F}$ for $\text{C}1$ and $1\mu \text{F}$ for $\text{C}2$ works well.

These regulators also limit current and protect themselves when the temperature exceeds the junction temperature. If you connect high current loads, expect the IC to get very hot quickly and eventually shut down. In that case, use a high current regulator like the 7805.

Besides using it as a voltage regulator, the IC can also function as a current regulator, a short-circuit protector, a booster circuit, and even a variable voltage regulator. You can find circuits for all these applications on page $27/45$ in the $\text{78L05}$ datasheet given below.

78L05 Applications

• Regulates to a constant $+5\text{V}$ output to power small loads (under $100\text{mA}$).
• Functions as an Adjustable Output Regulator.
• Acts as a Current Limiter for certain applications.
• Forms an Output Polarity-Reversal-Protection Circuit.
• Can be used in an Output Booster Circuit.

2D model of component (TO-92)