
26 2
Analog Electronics
vicious circle. The more voltage thrown away
across the emitter resistors, the lower the effici-
ency of the supply but the better the suppression of
current hogging.
Figure 10.13b shows two forms of overvoltage
protection or
crowbar.
This is commonly found in
a stabilized power supply designed to produce a
fixed output voltage, to supply a computer, for
instance. Should the pass transistor fail short-
circuit, or should a failure in the control circuit
result in the pass transistor being turned on hard, a
lot of expensive ICs could bite the dust. Any safety
circuit designed to prevent this should, in the
interests of