What is LM336-2.5 shunt regulator diode? This article will discuss the LM336-2.5’s basics, pin configuration, internal operation, specifications, features, working circuits, applications, and safe operating practices.

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LM336-2.5 Diode Basic

The LM336-2.5 Shunt Regulator Diode from Texas Instruments is a precision voltage reference designed to provide a stable 2.5 V output for analog and mixed-signal circuits. It functions like a high-accuracy Zener diode, but with much better voltage regulation and temperature stability.

This device operates in a shunt configuration, maintaining a constant reference voltage as long as the proper current is supplied. It offers low temperature drift and can be externally adjusted for fine voltage trimming, making it suitable for accurate and reliable designs.

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LM336-2.5 Diode Symbol

LM336-2.5 Diode Pinout Details

D Package (SOIC-8, Top View)

In the SOIC-8 package, only three pins are electrically active. Pin 4 is the Anode, Pin 8 is the Cathode, and Pin 5 is the Adjust (ADJ) pin used for fine-tuning the reference voltage. The remaining pins (1, 2, 3, 6, and 7) are marked NC, meaning no internal connection and should be left unconnected on the PCB.

LP Package (TO-92, Top View)

In the TO-92 (LP) package, the three leads are clearly labeled as Anode, Cathode, and ADJ. This package is commonly used for through-hole designs and simple reference circuits.

Alternatives & Equivalent Model

LM136-2.5

LM236-2.5

LM336B-2.5

LM185-2.5

LM285-2.5

LM385-2.5

LM4040-2.5

LT1009

TL431

LM336-2.5 Diode Schematic Diagram

This schematic shows the internal circuitry of the LM336-2.5 Shunt Regulator Diode, illustrating how it generates a stable 2.5 V reference rather than behaving like a simple Zener diode. Inside, multiple bipolar transistors (Q1–Q14) form a precision reference core, current sources, and gain stages that tightly control the voltage between the cathode and anode.

The left side of the diagram mainly handles voltage sensing and temperature compensation. Matched transistor pairs and small capacitors help cancel temperature effects and reduce noise, which is why the LM336 is much more stable than a standard diode reference. These internal elements ensure the reference voltage remains consistent over changes in current and temperature.

On the right side, the circuitry connected to the ADJ (adjust) pin allows fine trimming of the output voltage. By adding an external resistor, users can slightly adjust the 2.5 V reference or optimize temperature performance, making the LM336-2.5 suitable for precision analog applications.

LM336-2.5 Diode Specifications

LM336-2.5 Diode Features

Low temperature coefficient

Wide operating current range (400 µA to 10 mA)

Low dynamic impedance (≈0.27 Ω)

±1% voltage tolerance available

Specified temperature stability

Easily trimmed for minimum temperature drift using ADJ pin

Fast turn-on response

Precision 2.5 V shunt voltage reference

Better accuracy and stability than standard Zener diodes

Low noise performance suitable for analog circuits

Adjustable output voltage via external resistor

Good long-term stability and reliability

Available in through-hole and surface-mount packages

Simple two-terminal operation with optional adjustment pin

LM336-2.5 Diode Working in Circuit

LM336-2.5 as a 2.5 V Reference with Minimum Temperature Coefficient

In this circuit, the LM336-2.5 is used as a precision shunt voltage reference powered from a 5 V supply. The series resistor limits current into the device so it operates within its recommended range. The output node provides a stable 2.5 V reference, which is taken across the LM336-2.5. The two small signal diodes and the adjustable resistor connected to the ADJ pin allow fine trimming of the reference voltage and temperature coefficient. By adjusting this network, the circuit minimizes voltage drift over temperature, making it suitable for precision analog applications such as ADC references and calibration circuits.

LM336-2.5 as a Wide-Input-Range Reference

In this configuration, the LM336-2.5 works with an LM334 current source to create a stable 2.5 V reference over a wide input voltage range (about 3.5 V to 40 V). The LM334 sets a constant current through the LM336-2.5, ensuring proper regulation regardless of supply variations. As long as sufficient current flows, the LM336-2.5 maintains a steady 2.5 V output to ground. This makes the circuit ideal for systems with unregulated or varying supply voltages where a reliable reference is still required.

LM336-2.5 Diode Applications

• Precision voltage reference circuits

• Power supply voltage regulation

• Analog-to-digital converter (ADC) reference

• Digital-to-analog converter (DAC) reference

• Voltage monitoring and supervision circuits

• Sensor signal conditioning

• Instrumentation and measurement equipment

• Calibration and test equipment

• Battery-powered electronic systems

• Industrial control and automation circuits

• Data acquisition systems

• Comparator and op-amp reference sources

LM336-2.5 Diode Safely Operation

Operate the LM336-2.5 within its specified limits to ensure safe and reliable performance. Keep the operating current between 400 µA and 10 mA and always use a series resistor to limit current, as direct connection to a voltage source can damage the device. Ensure correct polarity, since reversing the anode and cathode may cause failure. Manage thermal conditions by avoiding excessive current and high temperatures, and use proper PCB layout for heat control. When using the ADJ pin, keep trimming resistor values within recommended ranges to maintain stability and accurate 2.5 V output.