The LM (linear monolithic) series ICs were invented by National Semiconductor. In the LM series, the linear monolithic refers to the analog components incorporated into a single silicon chip. Generally, these ICs include op-amps, differential comparators, instrumentation amplifiers, current mode amplifiers, voltage regulators, audio amplifiers, V to I converters, and many more. There are LM78xx & LM79xx series voltage regulators where the LM78xx series has positive output voltage and LM79xx series voltage regulators have negative output. The LM series voltage regulators are used frequently in different electronic projects & appliances. This article provides brief information on the LM78xx series voltage regulator namely; the LM7812 voltage regulator.
What is the LM7812 Voltage Regulator?
LM7812 is a positive voltage regulator chip from the LM78xx series and is available in a TO-220 package. This voltage regulator has a synchronous rectification feature and also wide frequency response. This voltage regulator IC offers a fixed 12Volts output voltage but the input voltage of this IC should not be > 35V < 14V because 35V is the maximum input voltage that it can handle. This voltage regulator IC is mainly designed for fixed o/p however the output can be adjusted easily if mandatory by the user using two external resistors only at the output.
The maximum load this IC can handle is 1A to 1.5A however the input current must be 2A to obtain 1A – 1.5A at the o/p. When this IC steps down the input voltage or performs voltage regulation then the voltage difference between the input & output voltages can be changed to heat so an appropriate heat sink is necessary for proper IC functioning.
Working
The LM7812 voltage regulator is mainly designed to offer 12V of stable output voltage. This IC simply works through a voltage divider circuit. It compares the applied i/p voltage to a reference voltage & regulates the o/p voltage accordingly. The voltage regulator IC has in-built thermal protection as well as current limiting for protecting the device from the conditions of overcurrent & overheating. This IC is commonly used where a fixed voltage source is necessary like; audio equipment, electronic devices, power supplies, etc.
Pin Configuration:
The pin configuration of the LM7812 voltage regulator is shown below. This IC includes three pins and each pin is discussed below.
LM7812 IC Pin Configuration
- Pin1 (IN): This is a positive (+ve) i/p voltage pin.
- Pin2 (GND): This is a Ground (GND) pin.
- Pin3 (OUT): This is a positive (+ve) o/p voltage pin.
Features & Its Specifications:
The features and specifications of the LM7812 voltage regulator are discussed below.
- LM7812 voltage regulator has three terminals.
- Its input voltage ranges from 14Volts to 35Volts.
- Its o/p voltage ranges from 11.75Volts to 12.25Volts DC
- Its typical o/p current is 1A.
- Its peak current is 2.2A.
- Its Dropout voltage is 2V.
- This IC is available in TO-220, TO-263 and TO-252 Packages.
- Its o/p current is 1.5A.
- Its fixed & accurate o/p voltage is 12V.
- Its max i/p voltage is 35V DC.
- Its low standby current is 8mA only.
- Its o/p voltage tolerance is 5%.
- Its contact plating is Tin.
- Its type of mounting is Through Hole.
- Its terminal position is single.
- Its o/p voltage accuracy is 4 %.
- Its PSRR or Power Supply Rejection Ratio is 71dB.
- Equivalent LM7812 voltage regulator ICs are; LM340A-12 LM1084-12 & LM340-12. The replacement of the LM7812 voltage regulator is LM317.
How to securely use LM7812 IC within a Circuit?
To very securely use LM7812 IC within a circuit for a long time, it is recommended not to operate any load >1.5A. An appropriate heat sink must be used with it. Do not operate this IC in temperatures < 0 degrees Celsius & > +125 degrees Celsius. Always store this IC in temperatures> -65 degrees Celsius & < +150 degrees Celsius.
LM7812 Voltage Regulator Circuit
LM7812 is a DC voltage regulator that is used to step down DC voltage precisely based on the requirement of the circuit. Here we are going to design a linear voltage regulator circuit with LM7812 IC which is used to step down DC voltage to 12 Volts.
The required components to make this LM7812 voltage regulator circuit mainly include; LM7812 IC, 14V to 35V, 1 A DC supply, capacitors 100 µF/36 V & 10µF/16V, bread board, and connecting wires.
The connections of this LM7812 voltage regulator circuit follow as;
LM7812 Voltage Regulator Circuit
- First, place the LM7812 IC on the breadboard; connect pin-1 of this IC to the +ve input supply whereas pin-2 is connected to the negative i/p supply.
- Connect 100 µF capacitor in between pin1 & 2 and 10 µF capacitor in between pin2 & 3.
- Connect the multimeter or voltmeter’s positive terminal to pin-3 of the IC and the negative terminal is connected to pin-2 of the IC. Once the supply is turned ON the meter measures 12 volts.
Working
LM7812 voltage regulator circuit works as; whenever 14v to 35v input voltage is provided then IC provides 12Volts output. In the circuit, the DC input voltage is provided to pin1 & 2 whereas the output DC voltage can be obtained from pin2&3. Here, pin-2 is common for a negative terminal that is shown within the circuit diagram. For stable use of this voltage regulator IC, the input voltage should not go beyond 28v.
We know that 7812 IC is a linear voltage regulator and they drop power & emit it in the heat form. If we provide input as 15v 0.5 A to 7812 IC then it has 12 v 0.5 A of output. Thus the voltage drop of this IC is 3 Volts.
This IC is a very simple and no expensive solution for different applications. Check the input voltage or current while using this IC that should not go above the voltage or current rating of the IC. The input & output pins of this IC must be connected carefully because the reverse connection of pins may damage the regulator IC.
Advantages & Disadvantages
The advantages of the LM7812 voltage regulator include the following.
- These ICs are not expensive.
- It has an instant short circuit shutdown-based feature.
- It has an instant overheat shutdown feature.
- It is reliable to utilize within commercial devices.
- It has internal thermal overload protection.
- This IC does not need any component to saturate/ balance their o/p voltage.
- It is very easy to make & use
- It gives precise output voltage.
- It has maximum temperature tolerance.
- This IC includes a set of pins & connectors which helps in connecting it with various circuit boards & circuits on a particular board.
The disadvantages of the LM7812 voltage regulator include the following.
- LM7812 voltage regulator needs a heat sink.
- These regulators have low efficiency.
LM7812 Voltage Regulator Applications
The applications of this regulator include the following.
- This voltage regulator is used in 12V power supplies, voltage step-down circuits, battery chargers, motor drivers, solar power supplies, remote cars, toys, chargers for phones, microcontroller-based applications, power distribution circuits, current limiters, regulated dual supply, etc.
- The voltage regulators are used in LEDs, motors, electronic communications, load switches, flashlights, DC fans, etc.
- It is used in AC motor controllers, fire alarms, electronic security, etc.
- This voltage regulator IC is an appropriate OLED driver IC used for power handling.
- These are used in a wide range of OLED-based applications like; touch panels, LED driving lamps Display driver RFID tags, LCD backlights, Home appliances, LED blinkers, etc.
- These ICs can be used in combination with exterior components to get adjustable currents and voltages.
- These are used as fixed voltage regulators.
Please refer to this for the LM7812 Voltage Regulator Datasheet.
Thus, this is an overview of the LM7812 voltage regulator IC. This is a precise power transistor including the features of wide frequency response & synchronous rectification. This IC is considered a next-generation supply, wherever it offers the chance to progress the fixed single-phase supply efficiency while meeting the AC power system & multi-phase demands. This IC is a better choice, especially for monitoring battery voltage. LM7812 IC is a very popular linear voltage regulator used to generate constant 12Volts. This IC is very simple to utilize without any external circuitry for voltage regulation. This IC provides approximately 500 mA of current with no heatsink & it provides upto 1 A of current with a heat sink. Here is a question for you, what is LM7805 IC?