Texas Instruments LM334M/NOPB

Overview

LM334M/NOPB from Texas Instruments is a 3-terminal adjustable current source IC designed for precision biasing, temperature sensing, and low-power reference applications. It delivers programmable current from 1 μA to 10 mA with ±3% initial accuracy, operates over 1 V–40 V supply range, exhibits 0.02%/V current regulation, and features true 2-terminal operation in its basic configuration. It is widely used in remote temperature sensing circuits where wire resistance does not affect accuracy.

For engineers reviewing the LM334M/NOPB datasheet, LM334M/NOPB pinout, LM334M/NOPB application, or LM334M/NOPB equivalent, key selection considerations include its temperature-proportional current output (≈+0.33%/°C), minimal 67.7 mV sense voltage at 25°C, SOIC-8 package compatibility, and suitability for micropower bias networks, LED drivers, and ramp generators requiring stable current sources without external power rails.

Technical Context

The LM334M/NOPB functions as a floating two-terminal current source when configured with a single external resistor, drawing current into the V+ pin while referencing the R pin for internal bias control. Its core operation relies on a temperature-dependent 67.7 mV reference voltage across the R–V− terminals at 25°C, scaled linearly with absolute temperature (°K).

It supports both 2-terminal and 3-terminal modes: in 3-terminal mode, the R pin enables precise current programming and temperature compensation; reverse voltage tolerance up to 20 V allows AC-coupled operation. Thermal regulation is critical above 100 μA due to self-heating effects-junction temperature rise degrades current stability at ≈0.132% per volt across the device at 1 mA.

Key Specifications

Pinout & Package

LM334M/NOPB is housed in an 8-pin SOIC (Package D, JEDEC MS-012 variation AA), 1.75 mm max height, RoHS-compliant with Sn lead finish and MSL Level-1 rating. Pin 1 is marked by a beveled corner and located in Quadrant Q1 per tape orientation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable current source applications.

Compared with LM334Z/NOPB, LM334M/NOPB offers superior thermal performance and SMT compatibility; versus REF200AU, it trades fixed accuracy and dual outputs for full programmability and Kelvin-scaled sensing capability-making it irreplaceable in temperature transduction and adaptive bias roles.

Availability

LM334M/NOPB is available at Aetrix Electronics and suitable for remote temperature sensing, LED driver circuits, micropower bias networks, and precision ramp generation requiring stable component supply across industrial, instrumentation, and embedded OEM programs.

Supply support for LM334M/NOPB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies, with decades of heritage in precision linear ICs and industrial-grade reliability.

The LM334 series belongs to TI's legacy precision current source product line, engineered specifically for applications demanding temperature-proportional current output, low-voltage operation, and robustness in unregulated or battery-powered systems.

FAQ

What is the minimum operating voltage for LM334M/NOPB at 10 μA set current?

The LM334M/NOPB requires a minimum forward voltage of 0.8 V when programmed for set currents between 2 μA and 100 μA. At exactly 10 μA, this threshold applies directly-enabling operation from partially discharged single-cell batteries or low-dropout regulator outputs. This specification is verified in the Electrical Characteristics table under "Minimum Operating Voltage" with conditions 2 μA ≤ I_SET ≤ 100 μA.

How do I calculate the external resistor value for a 5 mA set current with LM334M/NOPB?

Use the formula R_SET = 67.7 mV / I_SET, yielding R_SET = 67.7 mV / 5 mA = 13.54 Ω. For 5 mA at 25°C, a standard 1% metal-film resistor of 13.3 Ω or 13.7 Ω is appropriate. Note that I_SET increases by ≈0.33%/°C, so final accuracy depends on R_SET's temperature coefficient-TI recommends <20 ppm/°C for ±1% slope stability over temperature.

Can LM334M/NOPB be used as a temperature sensor without calibration?

Yes-LM334M/NOPB inherently outputs current proportional to absolute temperature (I_SET = I_o × T/298 K), so at 25°C it delivers precisely 298 μA when R_SET = 227 Ω. Initial accuracy is ±3%, meaning raw output has ±3°C equivalent error. For uncalibrated use, this suffices in HVAC or industrial monitoring where ±3°C resolution is acceptable; for higher accuracy, a single-point gain trim at one temperature corrects both offset and slope simultaneously.

Does LM334M/NOPB support reverse polarity protection in AC applications?

Yes-LM334M/NOPB tolerates reverse voltages up to 20 V across V+–V−, drawing only a few dozen microamperes in reverse bias. This allows direct integration into AC-coupled circuits (e.g., line-powered sensors) where the device alternately conducts and blocks, acting as both rectifier and current source without external diodes. This behavior is specified in Absolute Maximum Ratings and confirmed in application Figure 32 (In-Line Current Limiter).

What is the purpose of the R pin on LM334M/NOPB, and is it required for basic operation?

The R pin exposes the internal 67.7 mV sense node and is optional for basic 2-terminal operation-where only V+ and V− are used with R_SET connected externally between them. However, the R pin becomes essential for 3-terminal configurations enabling temperature compensation, zero-drift design (via diode/resistor network), and improved regulation in high-precision applications. TI's Application Hints detail R pin usage in Figures 15 and 25–26.