IC voltage regulators are seeing rapidly increasing usage. The LM100, one of the first, has already been widely accepted. Designed for versatility, this circuit can be used as a linear regulator, a switching regulator, a shunt regulator, or even a current regulator. The output voltage can be set between 2V and 30V with a pair of external resistors, and it works with unregulated input voltages down to 7V. Dissipation limitations of the IC package restrict the output current to less than 20 mA, but external transistors can be added to obtain output currents in excess of 5A. The LM100 and an extensive description of its use in many practical circuits are described in References 1–3. One complaint about the LM100 has been that it does not have good enough regulation for certain applications. In addition, it becomes difficult to prove that the load regulation is satisfactory under worst-case design conditions. These problems prompted development of the LM105, which is nearly identical to the LM100 except that a gain stage has been added for improved regulation. In the great majority of applications, the LM105 is a plug-in replacement for the LM100.