The 52150/52175, which is a replacement for the 78HGA, is an adjustable 4-terminal positive voltage regulator capable of supplying in excess of 5.0 A over a 5.0 V to 24 V output range. Only two external resistors are required to set the output voltage. It is packaged in a hermetically sealed TO-3, and provides 50W power dissipation. The regulator consists of a monolithic chip driving a discrete series-pass element. A beryllium-oxide substrate is used in conjunction with an isothermal layout to optimize the thermal characteristics of each device and still maintain electrical isolation between the various chips. This unique circuit design limits the maximum junction temperature of the power output transistor to provide full automatic thermal overload protection. If the safe operating area is ever exceeded (Note 1), the device simply shuts down rather than fail or damage other system components. This feature eliminates the need to design costly regulators built from discrete components.