# The Role of Resistors in Electronic Circuits

Resistors are often perceived as components used for voltage division and current regulation, but their other uses in circuits are less well-known. Actually, resistors have many uses and in many cases, these functions are crucial for the circuit. Without the functions provided by resistors, the circuit would quickly become paralyzed and unable to continue operating, and other electronic components would also be affected. Here are the nine typical functions of resistors:

### Functions of Resistors ##### 1. Voltage Division Function of Resistors in Circuits

We know that the voltage division function of resistors is one of the most common applications. When a voltage U1 is too high, two resistors can be used to form a voltage division circuit, reducing the voltage to U2, which conforms to the voltage division formula U2=U1*R2/(R1+R2). This type of resistor in the circuit is generally referred to as a voltage dividing resistor.

##### 2. Shunt Function of Resistors in Circuits

The shunt function of resistors is generally used when the current flowing through a component is too large. A resistor can be paralleled with it to play a shunt role, in accordance with the current shunt formula: I=I1+I2. This type of resistor in the circuit is generally referred to as a shunt resistor.

##### 3. Damping Function of Resistors in Circuits

In the LC resonant circuit, the resistor R1 can be introduced to reduce the Q value and play a damping role. This type of resistor in the circuit is generally referred to as a damping resistor.

##### 4. RC Circuit of Resistors in Circuits

The circuit in which the resistor and capacitor are combined is called an RC circuit. In the figure, R1 and C1 form an RC series circuit, and R2 and C2 form an RC parallel circuit.

##### 5. Negative Feedback Function of Resistors in Circuits

Resistors can form various forms of negative feedback circuits. The resistor R1 in the circuit forms a feedback branch of a negative feedback circuit. This type of resistor in the circuit is generally referred to as a feedback resistor.

##### 6. Current Limiting and Protective Function of Resistors in Circuits

The resistor R1 is used to limit the current in the circuit to prevent the variable resistor from being adjusted to the minimum, making the base voltage of the transistor VT1 equal to the power supply voltage VCC. If so, VT1 will be damaged due to excessive base current. This type of resistor in the circuit is generally referred to as a protective resistor.

##### 7. Oscillation Damping Function of Resistors in Circuits

In some high-performance amplifiers, such a coupling circuit is used, that is, a small resistor R1 is connected in series in the coupling loop, which can prevent the circuit from oscillating at high frequencies. This type of resistor in the circuit is generally referred to as an oscillation damping resistor.

##### 8. Isolation Function of Resistors in Circuits

When the isolation resistor is connected between the sub-circuit A and sub-circuit B in the circuit, these two parts of the circuit can be isolated. This type of circuit structure is often used to isolate the power supply circuit and scanning circuit in black and white TV circuits. This type of resistor in the circuit is generally referred to as an isolation resistor.

##### 9. Current to Voltage Conversion Function of Resistors in Circuits

When the current flows through the resistor, a voltage is generated across the resistor. As shown in the figure, the collector load resistor R2 plays this role, converting the current flowing through the resistor R2 into a voltage output from UO. This type of resistor in the circuit is generally referred to as a collector load resistor.

The nine functions of resistors in circuits mentioned above are all very important. Engineers understanding these applications of resistors are very helpful in designing resistors. They can design very superior circuits and also effectively use resistors and optimize circuit design in combination with other electronic components.

### Classification of Resistors

Resistors can be classified according to their materials, manufacturing processes, power, accuracy, and other factors. The common classifications are as follows:

##### 1. Classification by Material

The resistance value of a resistor varies with different materials. Common materials include carbon film resistors, metal film resistors, metal oxide resistors, electrolytic capacitors, thermistors, etc.

##### 2. Classification by Manufacturing Process

The performance characteristics of resistors vary with different manufacturing processes. Common manufacturing processes include film resistors, ferrite resistors, wire-wound resistors, varistor, etc.

##### 3. Classification by Power

The power of a resistor is directly proportional to its size. The larger the power, the larger the volume. Common powers include 1/8W, 1/4W, 1/2W, 1W, etc.

##### 4. Classification by Accuracy

The accuracy of a resistor refers to the degree of deviation between the resistance value of the resistor and the nominal resistance value. Common accuracies include 1%, 2%, 5%, etc.

##### 5. Other Classifications

For example, they can be classified into reliable and high-voltage resistors according to the rated voltage, or surface-mount and plug-in resistors according to the packaging structure.

In conclusion, resistors play a very important role in circuits. They can limit current, reduce voltage, regulate current and power, generate heat, etc. Therefore, when designing circuits, the role of resistors must be fully considered, and appropriate resistors must be chosen to ensure the stable operation of the circuit.