LM199 Precision Voltage Reference IC: Features, Applications & Specifications

The LM199 is a high-accuracy, temperature-stabilized precision voltage reference IC originally developed by National Semiconductor and now available from Texas Instruments and other manufacturers. Known for its exceptional long-term stability and ultra-low temperature drift, the LM199 is widely used in high-end instrumentation, calibration equipment, industrial control systems, and precision analog circuits.

This article explains the basic features, working principle, applications, and technical specifications of the LM199 in an SEO-optimized format.

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What is LM199?

The LM199 is a buried-zener voltage reference that delivers a highly stable 7.0V reference output.
What makes the LM199 unique is its integrated heater and temperature control circuitry, which maintains the reference at a constant internal temperature—dramatically reducing temperature-induced drift.

This self-heated design allows the LM199 to achieve performance comparable to laboratory-grade voltage standards.

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Key Features of LM199

✔ 1. Temperature-Stabilized Buried Zener Reference

• Integrated heater maintains constant die temperature
• Minimizes temperature drift over wide ambient ranges

✔ 2. Highly Stable 7V Output

• Nominal output voltage: 7.0 V
• Extremely low long-term drift

✔ 3. Ultra-Low Temperature Coefficient

• Typically ≤ 2 ppm/°C
• Ideal for precision measurement systems

✔ 4. Excellent Long-Term Stability

• Drift as low as 20 ppm per 1000 hours
• Suitable for calibration and metrology

✔ 5. Low Noise Performance

• Buried-zener architecture provides low output noise
• Suitable for high-resolution ADCs

✔ 6. High Output Drive Capability

• Can source several milliamps of load current

✔ 7. Wide Supply Voltage Range

• Operates from 9V to 40V

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⚙️ How LM199 Works

The LM199 uses a buried zener diode as the voltage reference element.
Unlike ordinary references, it includes an internal heater transistor and temperature sensor that keeps the die at a constant elevated temperature (typically around 90°C).

This ensures:

• Minimal voltage variation due to ambient temperature changes
• Stable performance in harsh industrial environments

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Applications and Uses of LM199

Because of its exceptional stability, the LM199 is commonly used in high-precision analog systems:

1. Calibration Equipment

• Multimeters
• Voltage standards
• Precision test instruments

2. Industrial Instrumentation

• Process control
• Data acquisition systems
• High-accuracy analog controllers

3. High-Resolution ADC/DAC Systems

• 16-bit to 24-bit ADC references
• Precision DAC output stabilization

4. Laboratory Measurement Equipment

• Bench instruments
• Reference voltage sources

5. Military and Aerospace Electronics

• Stable performance under temperature extremes

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LM199 Technical Specifications

Parameter	Value
Reference Type	Temperature-stabilized buried zener
Output Voltage	7.0 V (nominal)
Supply Voltage Range	9 V – 40 V
Temperature Coefficient	≤ 2 ppm/°C
Initial Accuracy	±5 mV (typical)
Long-Term Drift	~20 ppm / 1000 hours
Output Current	Up to 10 mA
Noise	Very low
Operating Temperature	−40°C to +85°C
Package	TO-46 metal can
Warm-Up Time	Several seconds (heater stabilization)

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LM199 vs Standard Voltage References

Feature	LM199	Bandgap Reference
Temperature drift	Extremely low	Moderate
Long-term stability	Excellent	Average
Noise	Low	Moderate
Power consumption	Higher (heater)	Low
Cost	Higher	Lower

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⭐ Advantages of LM199

• Outstanding temperature stability
• Very low long-term drift
• High accuracy for precision systems
• Ideal for laboratory and industrial environments

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⚠️ Limitations of LM199

• Higher power consumption due to internal heater
• Requires warm-up time for best accuracy
• Larger package compared to modern ICs

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Final Summary

The LM199 is a premium precision voltage reference IC designed for applications where accuracy, stability, and long-term reliability are critical. Its temperature-controlled buried zener architecture makes it one of the most stable references available, even decades after its introduction.

If you are designing calibration instruments, high-resolution ADC systems, or industrial measurement equipment, the LM199 remains an excellent choice.