Which circuit has the potential to overcome the drawback of unprotected external pass transistor?
Q. Which circuit has the potential to overcome the drawback of unprotected external pass transistor from the excessive current from a shorted output in linear voltage regulators?- Published on 20 Oct 15a. Current Regulator
b. Current Limiter
c. Voltage Regulator
d. Voltage Limiter
ANSWER: Current Limiter
The current sensing resistor sets base-to-emitter voltage of transistor in current-limiting circuit, by evaluating the difference between the voltage across the external resistor and voltage across limiting resistor due to opposite polarities. If the value of current through the external pass transistor increases beyond maximum value due to shorted output, then the value of voltage across the limiting resistor reaches to 0.7V by turning ON the current limiting transistor.
Hence, it becomes feasible for the current limiting transistor to conduct the current away from the external pass transistor as well as regulator. This ultimately results in an occurrence of thermal overload to some extent by shutting down the regulator. Factually, overall internal protection of IC voltage regulator from thermal overload is a major stage taken into consideration from designing point of view.
