#699 LM336 Voltage Reference
Exploring the LM336 precision reference and testing the minimum temperature coefficient circuit design.
Notes
The LM336 is a precision adjustable voltage reference diode, commonly used for voltage regulation and calibration in analog and digital circuits. It provides a stable reference voltage of 2.5V, with the ability to fine-tune the output using an external resistor. Operating over a wide current range, it offers low temperature drift and excellent long-term stability, making it ideal for use in power supplies, ADCs, DACs, and sensor applications. Unlike standard Zener diodes, the LM336 provides better accuracy and lower noise, making it a reliable choice for precision voltage regulation.
Circuit Design
While the simplest use of the LM336 is inline with a 2.5kΩ resistor, the datasheet describes a 2.5V Reference with Minimum Temperature Coefficient. That’s is the circuit I’ve reproduced here.
Essentially, it just requires a pair of signal diodes in series with a 10kΩ trimmer to set the adjustment point.
- I’m using 1N60P Germanium Detector Diodes
See the schematic in EasyEDA
Testing the circuit on a breadboard, and I am able to get a very stable 2.5V. Note:
- the datasheet seems to indicate the ADJ point should be set to adjusted to 2.49 V, but I must be misunderstanding it, because
- (a) this doesn’t work and
- (b) it doesn’t seem possible while also keeping the cathode at 2.5V.
- instead, I trimmed the pot until I get precisely 2.5V on the cathode. At this point, the ADJ pin is at approximately half that (~1.21V), as I would expect.
Protoboard Build
I decided to put the circuit on a small piece of protoboard:
It works nicely as a simple breadboard module.
