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.