Why is transistor current controlled?

Why is transistor current controlled?

Basically, a bipolar transistor amplifies a small current entering the base to produce a large collector current. It is a current-driven device since the collector current is controlled via the base current. In this region, the collector current remains almost constant regardless of the collector-emitter voltage (VCE).

Is BJT voltage controlled current source?

BJTs can be thought of as voltage-controlled current sources, but are more simply characterized as current-controlled current sources, or current amplifiers, due to the low impedance at the base. Early transistors were made from germanium but most modern BJTs are made from silicon.

Why transistor is called current controlled and not voltage controlled device?

It is a current controlled device because the base current controls the flow of current from the emitter to collector. In the linear region of operation the collector current is controlled proportionally to the base current by a multiplier we call Beta.

What is current is controlled by?

A resistor controls current in same branch. The dependent sources show interdependence of different branches. i.e current through one branch controls voltage through some other branch or current through one branch controls current through some other branch.

How BJT and thyristor can be acted as current controlled device?

The bipolar transistor is an example of current controlled device. Here, a small current is passing through Base-Emitter junction, and this current opens a large flow of charge carriers through the other junction, in turn the transistor acting like a controlled valve.

How is transistor controlled?

A voltage or current applied to one pair of the transistor’s terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal.

Why FETs are called voltage control device?

FET is called voltage controlled device because, you can control the output current of it by varying voltage at gate but not by varying it’s current. Whereas BJT is called current controlled device because you can control it’s output current by varying current sourced to its base and not by voltage.

Is the BJT transistor a current controlled device or a voltage controlled device?

The output current is dependent on the input currents, or the collector current is controlled by the base current. So, a bipolar junction transistor is a current controlled device.

Why BJT is called bipolar junction?

device is often called the bipolar junction transistor because its operation requires that the negatively charged electrons and their positively charged counterparts (the holes corresponding to an absence of electrons in the crystal lattice) coexist briefly in the presence of one another.

Is current controlled by a load?

Consequently, the current flowing through a load is generally determined by the amplitude of the applied voltage and the load’s current–voltage characteristics. In the case of an ordinary resistive load, the current–voltage relationship is simply the resistance. Thus, current equals voltage divided by resistance.

In which mode a BJT works as a current controlled current source?

BJT is current controlled due to the relationship between input (base current) and output (collector current). Ic = BETA*Ib. Where BETA is relatively constant over several decades of current. The MOSFET controls the channel charge based on the gate bias voltage (relative to source & bulk).

Is BJT a current controlled device or voltage controlled device?

The terms current controlled device and voltage controlled device are ambiguous. Book by author Donald Neamen refers BJT as voltage controlled current device. According to me, in case of BJT the output current NEEDS to be controlled by a continuous current I.The moving charge maintains the barrier.

What is constant base current in BJT?

A BJT operated with a constant base current acts, to a degree, like a current source in that if you apply a particular base current and vary the collector-emitter voltage from zero to a larger value within the current and power range of the transistor, you will find that the collector current rises as the collector-emitter voltage first rises (

What is the difference between a BJT and an FET?

In FET, output current depends on input voltage, so voltage controlled device. In bjt the base current controlles the flow of majority carriers from emitter (E) to collector (C) via base (B)e.g Take npn transitor and emitter base (EB)are fwd biased whereas base collector (BC) is reverse bias.

How does a BJT amplifier produce voltage?

If a voltage comes out of a BJT based amplifier that voltage is either the BJT’s collector current which is turned into a voltage by a resistor connected to the BJT’s collector orthe BJT is used as a voltage buffer (common collector or emitter follower) where it does not provide any voltage amplification but is does provide current amplification.