The TLP590B(C.F) is a photovoltaic output photocoupler from Toshiba in DIP-6 designed specifically for driving MOSFET gates in isolated solid-state relay (SSR) applications. When LED current flows through pins 1-2 (typically 10-20mA), the infrared LED illuminates a series array of photodiode cells on the output side. Unlike conventional phototransistor couplers that provide a logic-level output, the photovoltaic array generates an open-circuit voltage of approximately 7-10V across pins 4-5, sufficient to fully enhance the gate of a standard MOSFET. The short-circuit current is approximately 5-10uA, which charges the MOSFET gate capacitance through a gate resistor. Turn-on time is typically 0.5-1ms (limited by the small photocurrent), making it suitable for DC and low-frequency AC switching, not high-speed PWM. The (C.F) suffix indicates a specific CTR (Current Transfer Ratio) binning grade. The 5000Vrms isolation voltage provides reinforced insulation between control and load circuits.