The onsemi MOC205R2M is a single-channel optoisolator with a DC input and a transistor-with-base output, housed in an 8-SOIC surface-mount package. It provides 2500Vrms galvanic isolation between input and output, which is typical for basic signal isolation in industrial controls, PLC I/O modules, and logic-level interfacing where the isolation requirement is moderate. The current transfer ratio (CTR) is specified at 40% minimum and 80% maximum at a forward current of 10mA — this range tells you the output transistor will saturate with a 10mA LED drive, but the exact gain varies by unit, so the downstream circuit must tolerate the spread. Output side can handle up to 30V across the transistor and 150mA continuous current, which covers driving small relays, logic inputs, or a low-side switch in a 24V control loop.
Speed and switching behaviour
The 400mV Vce saturation at the output transistor means the voltage drop across the collector-emitter when fully on is low enough to drive a 5V logic input directly without a pull-up resistor, as long as the load current is within the 150mA limit.
Lifecycle and sourcing posture
RoHS3 compliant, meaning it meets the latest EU restriction of hazardous substances directive without exemptions — no lead, no cadmium, no phthalates in the bill of materials.