Overview

The LM10 (LM10CLN / LM10CN) is a landmark monolithic integrated circuit designed by legendary analog IC pioneer Bob Widlar for National Semiconductor (now Texas Instruments). Housed in an 8-pin through-hole DIP-8 and TO-99 metal can package, it combines an independent high-gain operational amplifier with a dedicated adjustable $200\text{ mV}$ precision voltage reference on a single chip.

The defining breakthrough of the LM10 is its extraordinary operating voltage envelope: it can operate reliably from a single supply as low as $1.1\text{V}$ DC (a single depleted NiCd, NiMH, or alkaline battery cell) up to $40.0\text{V}$ DC (or $\pm 0.55\text{V} \dots \pm 20\text{V}$ split supplies) while drawing just $270\ \mu\text{A}$ of quiescent current. With its common-mode input range extending to the negative rail ($V^-$) and an integrated reference buffer amplifier, the LM10 is renowned for 2-wire 4–20mA industrial current loop transmitters, floating battery monitors, low-voltage precision sensor amplifiers, and micropower linear voltage regulators.

Quick reference

Pinout (DIP-8 Package)

                            ┌───┴───┐
     (200mV Ref Out) REF OUT 1│ 1   8│ REF FEEDBACK (Ref Amp Feedback)
     (Op-Amp Invert)     -IN 2│ LM10│7│ V+ (+1.1V to +40V Supply)
     (Op-Amp Non-Inv)    +IN 3│     │6│ OUT (Op-Amp Output)
     (Negative / GND)     V- 4│DIP-8│5│ BALANCE (Offset Null)
                            └───────┘

Typical Application: 1.2V Single-Cell Battery Low-Voltage Monitor

Because the LM10 operates down to $1.1\text{V}$, it can accurately monitor a 1.2V / 1.5V battery cell without requiring any charge pumps or boost converters:

  +1.2V Single Battery Cell (V+) ────────────────────────┬─────────┐
                                                         │         │
                                                   [Pin 7: V+]     │
                                                      LM10         │
  [ 200mV Ref Out: Pin 1 ] ───► [Pin 3: +IN]                       │
                                                      │            │
  Battery Voltage Divider ────► [Pin 2: -IN]                       │
  (R1 = 100kΩ, R2 = 20kΩ)                             │            │
                                                [Pin 6: OUT] ──► [ Red Low-Battery LED ]
                                                [Pin 4: V-]        │
                                                      │            │
  Battery Negative (0V) ──────────────────────────────┴────────────┴── Battery Return

2-Wire 4–20mA Current Transmitter

The LM10 is uniquely capable of "floating operation" where the entire circuit is powered by the loop current itself:

  +24V Current Loop Supply ────────────────────────┐
                                                   │
                                          [Pin 7: V+]
                                             LM10  ───► [ Output Pass Transistor (BD139) ]
  Sensor Input Signal ──► [Pin 3: +IN]             │           │
                          [Pin 1: REF OUT] ────────┤           │
                          [Pin 4: V-] ─────────────┴───────────┴──► 4-20mA Current Loop Return

Common mistakes

• Leaving Reference Feedback (Pin 8) floating: Pin 8 is the inverting feedback input of the internal reference buffer. If using the default $200\text{ mV}$ reference, connect Pin 8 directly to Pin 1 (REF OUT). If setting an amplified reference (e.g. 1.0V or 2.5V), use a resistive divider between Pin 1 and Pin 8.
• Expecting high-speed performance: The LM10 is optimized for micropower, low-voltage precision DC measurement, with a gain-bandwidth product of approximately $300\text{ kHz}$. It is not intended for high-speed audio or RF signal processing.

Notes

• Suffix Guide: LM10CLN / LM10CN denotes commercial temperature range ($0^\circ\text{C} \dots 70^\circ\text{C}$) in standard plastic DIP-8; LM10H denotes hermetic TO-99 metal can.