This part is a kind of semiconductor called W20NB50.
Function of this product has STW20NB50.
Manufacturers : STMicroelectronics
Image and pinout :
Some of the text within the PDF file :
TA8221AHQ / ALQ TOSHIBA Bipolar Linear Integrated Circuit Silicon Monolithic TA8221AHQ,TA8221ALQ 30W BTL × 2Ch Audio Power Amplifier The thermal resistance θj−T of TA8221AHQ, TA8221ALQ package designed for low thermal resistance, has a high efficiency of heat radiation. The temperature rise of chip can be reduced, and the influence from the degradation of the features due to the temperature rise at the high output can also be reduced. This stereo audio power IC, designed for car audio use, has two built−in channels to reduce the characteristic difference between L and R channels. It also contains various kind of protection. TA8221AHQ TA8221ALQ Features • • Low thermal resistance : θj−T = 1.5°C / W (infinite heat sink) High power : POUT (1) = 30W (typ.) / channel (VCC = 14 [ ... ]