Why is an external pass transistor used in a voltage regulator?

The external pass transistor increases the available load current by creating an additional path from input to output. The path in this case was designed for an additional 150mA, but you can obtain larger output currents by substituting other components in the circuit.

How can a transistor be used as a voltage regulator?

The transistor works as a variable resistor regulating its collector emitter voltage in order to maintain the output voltage constant. The figure below shows the transistor series voltage regulator. With the input operating conditions, the current through the base of the transistor changes.

Is voltage regulator and transistor the same?

In very basic terms, a voltage regulator is a device for building a power supply, whereas a mosfet is something you use to build an amplifier. A voltage regulator is basically an integrated circuit that has several transistors within it, while a mosfet is exactly a single transistor.

Can you put voltage regulators in parallel?

To improve efficiency in high-power applications, voltage regulators can be used in parallel to double output current capability—if a means of forcing current sharing is provided. One circuit approach uses sense resistors in series with the load and is applicable to regulators of any type.

Why transistors are connected in series?

Two NPN transistors can be connected in series with the collector of the lower transistor connected to the emitter of the upper transistor, figure 4, which provides a way to switch off the load from two different signals. Either input can turn off the load but both need to be on for the load to be on.

What is the difference between a voltage regulator and a rectifier?

Perhaps the biggest thing to note is that a rectifier converts input AC power into DC electrical power. Regulators are, on the other hand, systems configured to automatically maintain a constant voltage level to protect various apparatus against damage that can be caused by fluctuating voltage.

What is transistor regulator?

Transistor Series Voltage Regulator : Circuit Design and Its Operation. In a power supply system, a regulator is an essential component, used to control the output power in power electronics. The power electronics can be defined as the control as well as the conversion of electrical power in the part of electronics.

Can you combine voltage regulators?

Current sharing with linear regulators is traditionally not as simple as connecting the parts in parallel. Two voltage reference-based linear regulators set to the same output voltage and with the outputs tied together will not share current equally.

How do you wire two voltage regulators together?

The normal method is to simply run the output of the two regulators through a diode (one each), and then connect the outputs of the diodes together. In this case, this is called a “Wired OR” and the diodes referred to as “OR-ing Diodes”. The diodes are there mainly to isolate one regulator from the other.

What are the limitations of voltage regulator?


  • Mechanical drive components, brushes and contractors require regular maintenance and/or replacement.
  • Frequent overloads can damage brushes.
  • Speed of voltage correction correct may not be fast enough for electronic loads.

How does a voltage regulator with transistor work?

A voltage regulator with transistor usually consists of a bipolar junction transistor (bjt) with high current handling capability in an emitter follower configuration, driven by zener diode and resistor potential divider (PD) network. We first use a Zener diode and resistor across the input rail to make a PD that provides a regulated output.

What are the limitations of transistor voltage regulators?

Limitations of Transistor Voltage Regulators. The steady and stabilized output voltage that is obtained from the regulator is limited to a voltage range of (30-40) Volts. This is because of the small value of the maximum collector emitter voltage of transistor (50 Volts).

What is the output voltage of a series regulator?

The output voltage of the series regulator is Vout = Vzener – Vbe. The load current Iload of the circuit will be the maximum emitter current that the transistor can pass. For a normal transistor like the 2N3055, the load current can go upto 15A.

What is a discrete transistor shunt voltage regulator?

The block diagram of a discrete transistor shunt voltage regulator is given below. As the name says the voltage regulation is provided by shunting the current away from the load. The control element shunts a part of the current that is produced as a result of the input unregulated voltage that is given to the load.