Overview

The LM7805 (and TO-220 packaged L7805CV / LM7805CT) is the single most recognizable fixed linear voltage regulator IC in electronics history. Designed by Fairchild Semiconductor and produced by STMicroelectronics, Texas Instruments, and ON Semiconductor, it provides a stable, low-noise +5.0V+5.0\text{V} DC power supply rail from unregulated DC input voltages ranging from 7.0V7.0\text{V} to 35.0V35.0\text{V}.

Capable of delivering continuous output currents of >1.5 Amperes> 1.5\text{ Amperes} (with adequate heatsinking), the LM7805 includes internal thermal overload protection, short-circuit current limiting, and output transistor safe-area protection.

Quick reference

Regulator TypeFixed Positive Linear Voltage Regulator
PackageTO-220 (L7805CV) / TO-263 / DPAK
Pinout (TO-220 Front)Pin 1: Input (IN), Pin 2: Ground (GND), Pin 3: Output (OUT)
Fixed Output Voltage+5.0 V+5.0\text{ V} DC (±4%\pm 4\% tolerance across temperature)
Input Voltage Range (VINV_{IN})7.0 V7.0\text{ V} min to 35.0 V35.0\text{ V} max
Dropout Voltage2.0 V2.0\text{ V} (Requires VIN≥7.0VV_{IN} \ge 7.0\text{V} for 5V output)
Continuous Output Current (IOUTI_{OUT})>1.5 A> 1.5\text{ A} (with heatsink)
Ripple Rejection Ratio62 dB…78 dB62\text{ dB} \dots 78\text{ dB} at f=120 Hzf = 120\text{ Hz}

Pinout (TO-220 Package)

Looking at the front labeled face of the TO-220 package with metal tab at top and leads pointing down:

text
        ┌──────────────┐
        │ [LM7805 Tab] │  (Metal Tab connected internally to Pin 2 GND)
        ├──────────────┤
        │    LM7805    │  (Front Face)
        └─┬────┬────┬──┘
          1    2    3
         IN   GND  OUT
PinNameDescription
1INUnregulated DC input voltage pin (+7.0V to +35V DC)
2GND / TABGround reference (0 V, connected to heatsink tab)
3OUTFixed regulated +5.0V DC output pin

Specifications

ParameterSymbolMinTypMaxUnitConditions
Regulated Output VoltageVOUTV_{OUT}4.85.05.2V7.0V≤VIN≤20V,5mA≤IO≤1.0A7.0\text{V} \le V_{IN} \le 20\text{V}, 5\text{mA} \le I_O \le 1.0\text{A}
Dropout VoltageVdV_d—2.02.5VIOUT=1.0A,TJ=25∘CI_{OUT} = 1.0\text{A}, T_J = 25^\circ\text{C}
Peak Output CurrentIOSI_{OS}1.52.2—AShort circuit peak current
Quiescent CurrentIdI_d—4.28.0mATJ=25∘CT_J = 25^\circ\text{C}
Quiescent Current ChangeΔId\Delta I_d——0.5mA5mA≤IOUT≤1.0A5\text{mA} \le I_{OUT} \le 1.0\text{A}
Output Noise VoltageVNV_N—40—µV10 Hz≤f≤100 kHz10\text{ Hz} \le f \le 100\text{ kHz}

Standard Circuit & Capacitors

text
       +V_IN Unregulated Input (7.0V - 35V DC)
          │
       [Pin 1: IN]
        LM7805
       [Pin 3: OUT] ──────────────┬─────────────── +5.0V Regulated DC Output
          │                       │
       [Pin 2: GND]          [ C2 = 0.1µF Ceramic ]
          │                       │
   [ C1 = 0.33µF Ceramic ]       GND
          │
         GND
  • Input Capacitor (C1=0.33 μFC_1 = 0.33\ \mu\text{F}): Required if the regulator is located more than 2 inches from the main power supply filter capacitors.
  • Output Capacitor (C2=0.1 μFC_2 = 0.1\ \mu\text{F}): Improves transient response and prevents high-frequency self-oscillation.

Common mistakes

  • Supplying less than 7.0V input voltage: The LM7805 has a 2.0V2.0\text{V} dropout voltage. Supplying only 5.5V5.5\text{V} or 6.0V6.0\text{V} VINV_{IN} causes output voltage regulation to drop out below 5.0V5.0\text{V}.
  • Overheating without a heatsink: Dropping 12V to 5V at 1A creates PD=(12V−5V)×1A=7 WattsP_D = (12\text{V} - 5\text{V}) \times 1\text{A} = 7\text{ Watts} of heat. The TO-220 package will reach thermal shutdown (∼150∘C\sim 150^\circ\text{C}) in seconds without an external aluminum heatsink.

Notes

  • LM78xx Series Family: LM7805 (5V), LM7808 (8V), LM7809 (9V), LM7812 (12V), LM7815 (15V), LM7824 (24V). Negative voltage equivalents belong to the LM79xx series (e.g. LM7905).

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