The fundamental challenge of power supply design is tosimultaneously realize two conflicting objectives: goodelectrical performance and low cost. The UC3842/3/4/5is an integrated pulse width modulator (PWM) designedwith both these objectives in mind. This IC provides designersan inexpensive controller with which they can obtainall the performance advantages of current mode operation.In addition, the UC3842 series is optimized for efficientpower sequencing of off-line converters, DC to DCregulators and for driving power MOSFETs or transistors.This application note provides a functional description ofthe UC3842 family and highlights the features of each individualmember, the UC3842, UC3843, UC3844 andUC3845 Throughout the text, the UC3842 part numberwill be referenced, however the generalized circuits andperformance characteristics apply to each member of theUC3842 series unless otherwise noted. A review of currentmode control and its benefits is included and methodsof avoiding common pitfalls are mentioned. The finalsection presents designs of power supplies utilizingUC3842 control