Precision Current Regulation Made Simple: J500 & SST500 Diodes
When designing circuits for test instrumentation, medical electronics, or any system where stable, low current is crucial, the choice of a current-regulating diode (CRD) can make all the difference.
Linear Systems’ J500 and SST500 series provide engineers with reliable, tightly specified constant-current performance — even across wide voltage and temperature ranges — while simplifying circuit design.
What is a Current Regulating Diode?
A current-regulating diode (also called a constant current diode) is a two-terminal device that limits current to a fixed value, regardless of voltage fluctuations within its operating range.
Internally, most CRDs use a JFET with the gate tied to the source. Once the device reaches saturation, the current remains steady over a wide voltage swing. This gives designers a simple, compact, and reliable current source without additional circuitry.
Key advantages:
Reduced part count compared to op-amp or resistor-based current sources
Stable performance across voltage changes
Compact and easy to integrate in low-power and battery-driven designs
The J500 & SST500 Series at a Glance
Feature | J500 Series | SST500 Series |
Package | TO-92 (through-hole), plus bare die | SOT-23 (surface mount), plus bare die |
Current Range | ~0.19 mA to 5.6 mA (nominal) | ~0.19 mA to 5.6 mA (nominal) |
Operating Voltage | Up to 50 V | Up to 50 V |
Temperature Range | −55 °C to +150 °C | −55 °C to +150 °C |
Forward Capacitance | ~2.2 pF (typical) | ~1.5 pF (typical) |
Why It Matters
Tight, predictable performance — essential for sensitive applications in medical instrumentation and precision test gear.
Package flexibility — TO-92 for prototyping and robust handling, SOT-23 for space-constrained SMT designs.
High reliability — Wide voltage and temperature ratings ensure stable performance even in harsh environments.
Simplified design — Drop-in constant current without biasing networks or active components.
Application Examples
Driving LEDs or photodiodes with a fixed current, even as supply voltage changes
Providing a stable bias for RTDs, thermistors, or strain gauges
Current sources in battery-powered medical devices
Simplifying constant-current references in test and measurement equipment
Choosing Between J500 & SST500
Prototyping / through-hole builds → J500 (TO-92 package)
Compact SMT designs → SST500 (SOT-23 package, lower parasitics)
Custom packaging or tighter screening → Bare die options available directly from Linear Systems
Final Thoughts
Linear Systems’ J500 and SST500 current regulating diodes deliver stable, predictable current regulation in easy-to-use packages. With options ranging from TO-92 to SOT-23 to bare die, and current levels spanning ~0.19 mA to 5.6 mA, these CRDs simplify circuit design while ensuring high performance across demanding applications.
📄 Explore datasheets on our Current Regulating Diodes page
✉️ Contact our applications team at support@linearsystems.com for design guidance
📦 Request samples to evaluate the J500 and SST500 in your next design
Prefer to speak with someone directly? Give us a call at (510) 490-9160 and our team will connect you with the right person.
