Do transistors work with AC current?

Do transistors work with AC current?

yes, transistors work with alternating signals too. Small signal that is what a transistor is designed to do. small AC signal means that a transistor operates with relatively small variations around its operating point, which makes it possible to consider the operation as linear.

How a BJT is used to amplify the AC signals?

This circuit uses a pair of resistors as a voltage divider to control exactly how much voltage is placed across the base and emitter of the transistor. The AC signal from the input is then superimposed on this bias voltage to vary the bias current. Then, the amplified output is taken from the collector and emitter.

Why do we perform both AC and DC Analyses for BJT what is its significance?

AC analysis gives u the output and other values when an A.C supply is provided to the designed circuit. DC analysis gives u the output and other values when an D.C supply is provided to the circuit. This tells you what would happen if you simply turned the circuit on and applied no signal to it.

Which is used for BJT switching operation?

The three terminals of BJT are base, emitter and collector. BJT is either a PNP transistor or NPN transistor based on the doping type of the three terminals. Using the transistor as a switch is the simplest application of transistors. The transistor acts as a switch in the cut-off mode and the saturation mode.

Can transistor be used as AC switch?

When using the transistor as a switch, a small Base current controls a much larger Collector load current. When using transistors to switch inductive loads such as relays and solenoids, a “Flywheel Diode” is used. When large currents or voltages need to be controlled, Darlington Transistors can be used.

Do transistors work with AC or DC?

Transistor is nothing but a variable resistor. It will work on DC and AC. But the voltage between Base and Emitter (Vbe) must be more that 0.7V. If AC goes below 0.7V or negative the Base to Emitter diode will be reverse biased.

How does a transistor amplify AC?

A small AC voltage at the transistor base generates a small base-emitter current which is amplified by the transistor to give a larger AC collector current. This amplified collector current through the collector resistor creates an AC voltage that is greater than the input voltage, thus the input voltage is amplified.

What is AC analysis of BJT?

AC analysis of a common-emitter amplifier circuit begins by recognizing the capacitive reactance (XC) remains very low at the signal frequency. Because the AC source voltage has an internal resistance of zero ohms, the source voltage appears at the base of the transistor.

What is AC response?

Another aspect of the behavior of electronic devices which is of much interest to circuit designers is the small-signal ac response of the device. This is the response of the device to a small sinusoidal voltage imposed upon a generally much larger dc bias voltage.

When BJT is used as a switch and switch is said to be on when?

A switch offers open circuit (infinite resistance) when it is put in ‘OFF’ position and offers short circuit (zero resistance) when it is put in ‘ON’ position.

Can a BJT be used as an open switch?

When the BJT is operating in the cutoff region, then it could be used like an open switch while if it is operating in the saturation region, the BJT could be used as a closed switch. The BJT can be also used as an amplifier if you properly bias it to operate in the active or linear region.

What is the difference between BJT and unipolar transistors?

While Unipolar transistor i.e. field effect transistor uses only one type of charge carrier. BJT is a current controlled device. The current flows from emitter to collector or from collector to emitter depending on the type of connection. This main current is controlled by a very small current at the base terminal.

What is the cutoff region of a BJT circuit?

As shown again in figure 4, the BJT operates in the cutoff region when I B is equal to zero. In this case, there should be no current that will flow through the collector. However, in reality, there will be a very small collector leakage current that will flow due to the thermally produced carriers.

What is the working principle of the base BJT?

BJT is a current controlled device. The current flows from emitter to collector or from collector to emitter depending on the type of connection. This main current is controlled by a very small current at the base terminal.