Why do we need a resistor connected to the base of the transistor?

Why do we need a resistor connected to the base of the transistor?

why do we need a resistor connected to the base of the transistor? You only need a base resistor when you operate a transistor in the common emitter mode, and that, as has been said is to limit the base current to protect both the transistor and the arduino output.

How do you calculate the base resistance of a transistor?

To calculate the base resistor, subtract the B-E 0.7V from the driver voltage and divide by the base current: 4.5-0.7 = 3.8V / 400uA = ~9.5K ohms max. The difference in CE drop between a factor of ten and using the beta is neglible for relatively slow on/off circuits, and it lowers the driver current requirement.

How do you calculate the operating point of a transistor?

Every transistor circuit has a load line. If the base resistance is given you can also calculate the current and voltage for the operating point. By plotting IC (2.9 mA) and VCE (6.3V), we get the operation point —-> Q-point (quiescent point).

What is base resistor?

Consider a base resistor that controls the amount of current entering the base junction of a bipolar junction transistor (BJT) to cause it to conduct in the saturation region. For hard saturation, engineers usually use a DC current gain hFE value of 10. …

How do you calculate base voltage?

This can be done using the formula: Vcc = Vrc + Vrb + Vbe + (Ic + Ib)Rc + IbRb + Vbe, where “Vrc” is the voltage across the collector resistor; “Vrb” is the voltage across the base resistor (connected across the base) and the junction between the collector resistor and the transistor collector; and “Vbe” is the voltage …

Where is PNP transistor used?

PNP transistors are used as switches. PNP transistors are used in amplification circuits. PNP transistors are used in Darlington pair circuits. PNP transistors are used in robotic applications.

What is the working of PNP transistor?

The PNP transistor turns on when a small current flows through the base. The direction of current in PNP transistor is from the emitter to collector. The letter of the PNP transistor indicates the voltage requires by the emitter, collector and the base of the transistor.

How do you wire a PNP transistor?

First of all, to turn on the PNP transistor, you need the voltage on the base to be lower than the emitter. For a simple circuit like this, it’s common to connect the emitter to the plus from your power source. This way, you know what voltage you have on the emitter.

When PNP transistor is used as an amplifier?

Solution : When NPN transistor is used as an amplifier, majority charge carriers electrons of N-type emitter move from emitter to base and than base to collector. Step by step solution by experts to help you in doubt clearance & scoring excellent marks in exams.

Which of the following is true for PNP transistor?

Which of the following are true for a PNP transistor? Explanation: The 2 – 5% of holes is lost in recombination with electrons in the base region. The majority charge carriers are holes for a PNP transistor. Thus the collector current is slightly less than the emitter current.

Which region of the transistor is highly doped?


What is the relation between alpha and beta of a transistor?

A transistors current gain is given the Greek symbol of Beta, ( β ). As the emitter current for a common emitter configuration is defined as Ie = Ic + Ib, the ratio of Ic/Ie is called Alpha, given the Greek symbol of α.

In which region a transistor acts as an open switch?

Cutoff Region

How does a BJT act as a switch?

If the transistor is biased into the linear region, it will operate as an amplifier or other linear circuit, if biased alternately in the saturation and cut-off regions, then it is being used as a switch, allowing current to flow or not to flow in other parts of the circuit.

Can a transistor be used as a switch?

One of the most fundamental applications of a transistor is using it to control the flow of power to another part of the circuit — using it as an electric switch. Driving it in either cutoff or saturation mode, the transistor can create the binary on/off effect of a switch.

How do you saturate a transistor?

A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation. Consider this Common Emitter Amplifier circuit.

Why VCE SAT is 0.2 V?

transistor vce voltage drop It is because both the junctions in the transistor are forward biased at saturation. Under this condition, for npn transistor the emitter to base voltage is ~+0.7V and than between the base to collector ~0.5V (base p, collector n).

How much power can a transistor handle?

As the (oh so fuzzy) datasheet on that site says, the (SS9013) transistor can withstand 20V across C-E and 500mA total. As long as you don’t exceed those you should be fine.

What is IC saturation?

Saturation is when the current and voltage rise almost linearly together for a fixed base current. https://electronics.stackexchange.com/questions/129408/current-in-saturation-and-active-regions-of-bjt/6.

What is the ratio of IC to IE *?

So the current ratio IE/IB is very large (IE/IB = (β + 1)). BJT Current Components: Collector Current IC is composed of electrons that diffuse from the emitter across the forward biased base-emitter junction, which then continue to diffuse across the base region.

What is the ratio of IC to IE?


What happens when a transistor is saturated?

Saturation is the on mode of a transistor. A transistor in saturation mode acts like a short circuit between collector and emitter. In saturation mode both of the “diodes” in the transistor are forward biased. That means VBE must be greater than 0, and so must VBC. In other words, VB must be higher than both VE and VC.

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