Profile: ON Semiconductor Corp. is a supplier of semiconductors and integrated circuit devices. Our product line includes bipolar transistors, diodes & rectifiers, thyristors, drivers, converters and regulators. Our series of bipolar digital transistors is designed to replace a single device and its external resistor bias network. The bipolar digital transistor contains a single transistor with a monolithic bias network consisting of two resistors; a series base resistor and a base-emitter resistor. This eliminates these individual components by integrating them into a single device and can reduce both system cost and board space. Our NCP1236 is a new fixed-frequency current-mode controller featuring Dynamic self-supply (DSS). This device is pin-to-pin compatible with the previous NCP12xx families. The DSS function greatly simplifies the design of the auxiliary supply and the VCC capacitor by activating the internal startup current source to supply the controller during transients.