Theory o f O peration-60a
amplifier system similar to that just described for the
+ 1 5-Volt R egulated Supply.
The cent er of resistive-divider network R 978-R979 is
set by t he error amplifier to be zero volts, with respect
to ground, during norma l operation. Any variation in
output from the - 1 5-Volt Regulated Supply is coupled
to the error amplifier, which changes the bias of the
- 1 5-volt
regulator (0976). This change in bias,
and
change in conduction of the regulator,
nullifies the output variation to maintain a steady level
from the supply.
4- 10
Diode C.R993 protects the - 1 5-volt series regulator
(0976). If excess current is demanded from this supply.
Essentia lly, all current from this supply flows through
R975. When excess current is demanded from the
- 1 5-volt series regulator, due to a short circuit or
similar malfunction at the output of this supply, the
voltage drop across R954 increases enough to forward
bias C R993. This increases the conduction of 0994
which then reduces the conduction of 0976 to limi
t
the supply current to a safe level. Fuse F955 provides
circuit protection in the event of an overload or
regulator malfunction.
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