This part is a kind of semiconductor called UC3842.

Function of this product has Current-mode PWM controller.

Manufacturers : Philips

Image and pinout :

Some of the text within the PDF file :

Philips Semiconductors Linear Products Product specification Current-mode PWM controller UC3842 DESCRIPTION The UC3842 is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting. Protection circuitry includes built-in undervoltage lock-out and current limiting. Other features include fully-latched operation, a 1% trimmed bandgap reference, and start-up current less than 1mA. These devices feature a totem-pole output designed to source and sink high peak current from a capacitive [ ... ]

UC3842 PDF Datasheet Download