BUY BBY51 https://www.utsource.net/itm/p/11285066.html
BBY51 Variable Capacitance Diodes (Varicaps, Varactors) 7V 5.4pF 1.75 SOT-23/SC-59 marking S3 low tuning voltage
Package: SOT-23/SC-59
Manufacturer: Infineon
Description: The BBY51 is a low-power, high-speed, NPN switching transistor.
Features:
Low collector-emitter saturation voltage
Low noise
High switching speed
High current gain
Low collector-emitter leakage current
Applications:
Audio amplifiers
High-speed switching
Motor control
Power switching
(For reference only)