What is the role of a series pass transistor in a regulator?
In a linear voltage regulator, the pass transistor is the main element that is used to actually control the output voltage as the load current varies. As such, it acts like a variable resistance, regulating voltage by throwing away the excess as heat.
What is the difference between series and shunt regulator?
A series regulator is connected in series with the load to stabilize the regulator’s output voltage. A shunt regulator, on the other hand, is connected in parallel to the load to stabilize the device’s output voltage.
Why is the series type transistor pass better than the shunt type transistor pass?
Unlike the shunt voltage regulator, the series regulator does not draw the full current even when the load does not require any current. As a result the series voltage regulator is considerably more efficient.
What are the advantages of shunt voltage regulator over a series voltage regulator?
- The transistor shunt regulator has a good efficiency for small load currents.
- It has eased to reject short circuit.
- The voltage regulation is good.
- It has constant DC output voltage.
Do you prefer a series or shunt voltage regulator Why?
Shunt voltage regulator has poor voltage is constant. Series voltages regulator has better voltage regulation. The control element has to bear the load voltage across it. So, it is a high voltage low current device.
What is the disadvantage of series regulator?
It has not so good voltage regulation for large loads currents. The series pass transistor should be power transistor and it has to be mounted on a suitable heat sink. This makes the series regulator circuit bulky and heavy.
What is the output voltage of the LM317 current regulator?
The output voltage of the regulator can be adjusted from 1.25V to 35V. However, the chip can deliver currents up to 1.5A which is not enough for some power applications. In this article, I will discuss two methods of LM317 current boosting, using power PNP and NPN pass transistors.
What is LM317 current boosting?
LM317 is one of the most popular adjustable regulator chips. The output voltage of the regulator can be adjusted from 1.25V to 35V. However, the chip can deliver currents up to 1.5A which is not enough for some power applications. In this article, I will discuss two methods of LM317 current boosting, using power PNP and NPN pass transistors.
How does the LM317 pass transistor work?
The amount of current sharing is established with a resistor placed in series with the 317 input and a resistor placed in series with the emitter of the pass transistor. In the figure below, the pass transistor will start conducting when the LM317 current reaches about 1 amp, due to the voltage drop across the 0.7 ohm resistor.