A resistor is a passive electrical component with two terminals; it limits the current passing through an electrical circuit. When connected to an electrical circuit, the resistor is fixed; meanwhile, the resistance of transistors or potentiometers is changeable.
Why Is the Base Resistor of a Transistor Important?
The base in a transistor has a specific voltage; if you try to provide it with a higher voltage, the base current will rise, and the transistor will burn out. For example, in a silicon BJT, the base emitter’s voltage is 0.7 volts; driving a voltage of more than 0.7 volts will burn the transistor.
This can be a problem if you are trying to supply the transistor with an output port of Arduino, as the port generates approximately 5 volts. This case can be imagined as if the transistor was a cable you want to pull while it has a “stop collar” that limits the distance you can pull to 0.7 inches.
You want to connect the cable to a hydraulic cylinder of a 5-inch stroke; connecting them without assistance will lead to the breakage of either the cable or the cylinder. Therefore, you must seek assistance; for example, a string “resistor” will connect the two components.
The spring “resistor” job is to absorb the difference between the cylinder and the cable and keep each of them safe. The resistor can be changed according to the difference; the more significant the difference, the bigger the resistor, and the energy absorbed by the resistor will be converted into heat energy.
What Are the Other Functions of a Resistor in Transistor Circuit?
The first thing resistors are used for in a transistor circuit, or any other electrical circuit, is limiting the current. The resistor is connected in series with any electrical component like a transistor to protect it from excessive current and transfer this energy into heat energy.
The resistor can be either a fixed or a variable resistor; the variable resistor provides more flexibility to the electrical circuit. It can be changed according to the current supplied to the circuit; meanwhile, fixed resistors must be changed if you wish to increase the supplied current.
Current and Voltage Diversion
You can use a resistor if you have two transistors and wish to diverge the current between them. Resistors diverge the current or shunt the circuit when connected in parallel with electrical components. For example, if the transistors are connected in series, connect a resistor in parallel, and the current will be divided.
The resistor will take a part of the current according to its resistance, and the rest will flow through the transistors. Transistors are like any electrical component with a rated voltage value; if the power supply is higher than the rated voltage, they can not be connected directly to this power supply.
You will need a resistor with a resistance that lowers the voltage to the required amount. To lower the voltage, the resistor must be connected in series with the transistors, known as voltage diversion.
Bias Voltage
The basis voltage is the voltage from the power supply to the base of a transistor. Resistors are connected between the power supply and the base of the transistor to regulate the voltage provided to the base. This voltage from the resistor to the transistor base is called bias voltage.
Negative Feedback, Oscillation, and Damping Effect
The negative feedback in a transistor circuit is formed by the feedback branch that arises from the resistance between the collector and base of the transistor. The resistors used in transistor circuits play the role of negative feedback in the circuit.
If the circuit has a capacitor beside the resistor, it will form an RC circuit, this type of circuit can be combined in series or parallel. For example, if you have LC resonant circuit and connect a resistor in parallel will reduce the Q value, and the resistor will play a damping effect.
Convert Electrical Energy into Heat Energy
When you connect a resistor in a parallel or series with a transistor, it will either diverge the current if connected in parallel or limit it if connected in series. As a result, the current the resistor draws will be converted into heat energy; this principle is used in many electrical applications like heaters and stoves.
What Are the Principles of Selecting a Resistor for Transistors?
When selecting a resistor for a transistor or any electrical component, you must follow some principles; you must choose resistors that can implement high-level standards and have a certification body. The second principle is to look for resistors with service, price, efficiency, quality, and functional advantages.
The last principle is to check the model catalog of any resistor you buy and ensure it follows the abovementioned requirements. If the resistor lacks any of these qualities, you will put your electrical components in danger, especially those that cannot bear any power surges.
Conclusion
To summarize, a transistor is a passive electrical component that consists of three parts the base, the collector, and the emitter. When looking at transistors in electrical circuits, you will find a resistor connected to its base emitter. The resistor is used for many reasons in electrical circuits of transistors.
The main reason a resistor is connected to the base of a transistor is to limit the current flowing through the base. This makes the main job of the resistor is transistor protection because if the current supplied to the transistor increased, it would burn the transistor out.
Another reason to connect a resistor to a transistor is to diverge the voltage across the transistor’s terminals. Resistors can also diverge the current or shunt the circuit when connected in parallel, the resistor connected to the transistor base is the primary provider of the bias voltage.
The last thing is to choose your resistor wisely before connecting it to your electrical circuit; it must have a certification body and some advantages like service, price, efficiency, quality, and functional advantages.
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I am Inemesit Etim and I am honest, reliable, confident, and responsible in my work. I am a highly talented, detail-oriented creative content writer with 3+ years of experience writing helpful content that gives value to readers like you. My articles are a product of intense research, both from personal experiences and from reading through the experiences of others. I love home improvement and I am glad I can help you improve the quality of your home and living experience.
