ILX Lightwave LDX-3525: Precision Current Source, 200/500 mA, LDX-3500B Series

The ILX Lightwave LDX-3525 is a microprocessor-controlled precision current source designed for laser diode control across the LDX-3500B series. It delivers stable, accurate current output in two selectable ranges - 200 mA and 500 mA - with exceptional setpoint resolution and accuracy. The instrument operates in three modes: Constant Current (CC) CW for low-bandwidth applications, high-bandwidth CC for modulation up to 500 kHz, and Constant Optical Power (APC) for closed-loop control.

Integrated photodiode current measurement (0–5000 µA range, 1 µA resolution) enables direct optical feedback. Multiple laser diode protection circuits - including independent hardware current limits, slow-start turn-on, output shorting relay with semiconductor switch, and adjustable voltage limits - ensure safe, reliable operation in research, development, and production environments.

Technical Specifications

• 200 mA or 500 mA selectable ranges


• Setpoint resolution: 50–100 µA (200 mA) / 125–150 µA (500 mA)


• Setpoint accuracy: ±0.1% of full scale (±0.2 mA / ±0.5 mA)


• Output current accuracy at 25°C: ±0.2 mA (200 mA) / ±0.5 mA (500 mA)


• Temperature coefficient: <50 ppm/°C


• Short-term stability (1 hour): <20 ppm at half-scale


• Long-term stability (24 hours): <50 ppm at half-scale


• Noise and ripple: <2 µA rms (CW) / <4 µA rms (modulation, 100 kHz bandwidth) Compliance & Power


• Maximum compliance voltage: 7 V


• Input power: 95–125 VAC or 210–250 VAC, 50–60 Hz Photodiode Measurement


• Current range: 0–5000 µA (0–5.000 mA)


• Resolution: 1 µA Modulation & Control


• Analog modulation input: Up to 500 kHz (differential input)


• Analog output for remote monitoring


• Calibration: Closed-case via front panel or USB 2.0; data stored in non-volatile memory

Key Features

• Microprocessor control with three operating modes (CC-CW, CC-HBW, APC)


• Independent hardware current limits with adjustable thresholds


• Slow-start turn-on and output shorting relay (normally closed) plus semiconductor switch


• Power line surge and EFT transient protection


• Intermittent contact protection

Typical Applications

• Laser diode testing and characterization


• High-speed modulation experiments


• Optical power stabilization


• Production-line laser driver validation

Compatibility & Integration USB 2.0 interface for control and calibration management; differential modulation input enables flexible ground configurations for multi-channel test setups.