The LM1921 Relay Driver incorporates an integrated power PNP transistor as the main driving element The advantages of this over previous integrated circuits employing NPN power elements are several Greater output voltages are available off the same supply for driving grounded loads typically 4 5 volts for a 500 mA load from a 5 0 volt supply The output can swing below ground potential up to 57 volts negative with respect to the positive power supply This can be used to facilitate rapid decay times in inductive loads Also the IC is immune to negative supply voltages or transients The inherent Safe Operating Area of the lateral PNP allows use of the IC as a bulb driver or for capacitive loads Familiar integrated circuit features such as short circuit protection and thermal shutdown are also provided The input voltage threshold levels are designed to be TTL CMOS and LSTTL compatible over the entire operating temperature range If several drivers are used in a system their inputs and or outputs may be combined and wired together if their supply voltages are also common