The 3 pin IC’s are generally used for LINEAR, FIXED and ADJUSTABLE output voltage regulator applications (FIXED POSITIVE, FIXED NEGATIVE AND VARIABLE TYPES). 78XX series IC regulator have intern overload protection and short circuit current limiting. Check your 78xx and 79xx series, 3 Pin Voltage Regulator ICs. Fixed Positive voltage type: 78XX series. Fixed Negative voltage type: 79XX series.