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LM7912CT

-12V 1A negative linear regulator, TO-220, thermal/SCP protection

8000

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Pieza del fabricante：

LM7912CT

Paquete：

TO-220-3 (10.16 x 4.7 x 20.4mm, through-hole, tab=GND)

Marca：

Categorías de productos：

Circuitos integrados IC, Microcontroladores y procesadores

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Descripción

Productos

The LM7912CT from onsemi is a 3-terminal 1A negative voltage regulator providing a fixed -12V output with internal thermal shutdown and short-circuit protection in a TO-220 package — the negative complement to the LM7812CT for split-rail supplies.

Especificaciones

Output Voltage	-12V fixed (±4% at 25°C)
Corriente de salida	1A continuous
Input Voltage Range	-14.5V to -35V
Dropout Voltage	2V typical @ 1A
Line Regulation	10mV typical
Load Regulation	15mV typical
Corriente de reposo	3mA typical
Ripple Rejection	60dB typical @ 120Hz
Temperatura de funcionamiento	-40°C to +125°C (junction)
Paquete	TO-220-3 (through-hole, tab=GND)

Características

Fixed -12V output
1A continuous output current
Internal thermal overload protection
Internal short-circuit current limiting
60dB ripple rejection
Complement to LM7812CT (+12V)

Aplicaciones

±12V split power supply
Op-amp negative rail
RS-232 negative supply
Audio amplifier ±12V

Introducción del producto:LM7912CT Presentación del producto

The LM7912CT from onsemi is the negative-voltage counterpart of the LM7812CT, providing a fixed -12V output at up to 1A. Together, the LM7812 (+12V) and LM7912 (-12V) form a complete ±12V split power supply, which is the standard supply voltage for operational amplifiers (NE5532, TL072, LM741), analog switches, and many other linear ICs. The negative regulator operates with a negative input voltage: the input must be more negative than -14.5V (at least 2.5V below -12V) to maintain regulation. The pinout differs from the 78XX: pin 1 is GND (not input), pin 2 is input (not GND), pin 3 is output. This pinout difference is critical — inserting a 7912 in a 7812 socket will damage the device. The tab is connected to GND (same as 7812), so both can share a common heatsink without electrical isolation. The CT suffix denotes the TO-220 package.

Principio de funcionamiento:LM7912CT Principio de funcionamiento

The LM7912CT operates identically to the LM7812CT but with all voltages negated. It uses a series pass transistor between the negative input and the -12V output, controlled by a feedback loop comparing the output voltage with an internal reference. When the output rises above -12V (toward 0V), the pass transistor is driven harder to pull the output more negative. When the output drops below -12V, the drive is reduced. The thermal protection disables the output when the junction temperature exceeds ~175°C. The current limiting restricts output during a short circuit. The 60dB ripple rejection attenuates input ripple by a factor of ~1000. Power dissipation: Pd = |VIN − VOUT| × IOUT = |-18V − (-12V)| × 1A = 6W, requiring a heatsink similar to the LM7812. Important: both input and output capacitors are required for stability — a 2.2µF tantalum at the input and 1µF at the output are recommended, placed close to the regulator.

Descripción de la clavija:LM7912CT Definición y funciones de las clavijas

Pin	Nombre	Tipo	Descripción
1	GND	Suelo	Common ground reference. The TO-220 tab is electrically connected to this pin. Note: 79xx negative regulators have GROUND on Pin 1 (opposite to 78xx where Input is Pin 1). Heatsink tab must be insulated when not at ground potential.
2	INPUT	Entrada de alimentación	Negative unregulated input voltage. Must be more negative than -1.2V – Vdropout (at least -3.2V input). Maximum -35V. Bypass with 2.2µF electrolytic or 0.33µF ceramic capacitor to GND.
3	OUTPUT	Potencia de salida	Regulated -1.2V DC output at up to 1.5A continuous current with ±4% tolerance. Bypass with 1µF tantalum or 10µF electrolytic capacitor to GND for stability. Do not apply positive voltage to output to prevent damage.

Critical note: 79xx negative regulators have DIFFERENT pin assignments from 78xx positive regulators. Pin 1 = GND (not Input), Pin 2 = Input (not GND), Pin 3 = Output. This pin swap is a common source of design errors. The tab is connected to GND (Pin 1). Always verify pinout against the datasheet before PCB layout.

Application Scenarios:In which products and applications isLM7912CT usado

±12V Op-Amp Supply: Transformer center-tap → GND; positive winding → bridge+filter → LM7812CT (+12V); negative winding → bridge+filter → LM7912CT (-12V); clean ±12V for NE5532, TL072, LM741
RS-232 Supply: LM7912CT provides -12V for MAX232 charge pump; combined with LM7812CT +12V
Audio Amplifier: ±12V rails from LM7812+LM7912; Class-AB push-pull output stage; symmetrical clipping

Alternative Models:What chips are recommended as replacements for LM7912CT

Modelo	Fabricante	Diferencia clave	Paquete	Specs
LM7912ACT	onsemi	Tighter output tolerance: ±2% vs ±4% for precision negative supply rails	TO-220-3	-1.2V/1A
L7912CV	STMicroelectronics	Direct equivalent with 1.5A output current and internal thermal/current protection	TO-220-3	-1.2V/1.5A
MC7912CTG	onsemi	Current production replacement with RoHS compliance and identical specifications	TO-220-3	-1.2V/1A
KA7912	onsemi/Fairchild	Budget-friendly version with ±4% tolerance for cost-sensitive negative supply designs	TO-220-3	-1.2V/1A
LM337T	TI	Adjustable -1.25V to -37V version providing flexible output voltage with two external resistors	TO-220-3	-1.25 to -37V adj

LM7912CT is a -1.2V fixed negative voltage regulator in TO-220-3 with 1A output and ±4% tolerance. For adjustable negative voltage, the LM337T provides -1.25V to -37V output. All 7912 variants share the same pinout (GND-IN-OUT) and are complementary to the 7812 positive regulators for split-rail supplies.