Why are resistors in parallel preferred over a single resistor in some circuits?

@bryan Using multiple resistors in parallel instead of a single resistor can offer several advantages, depending on the specific requirements of the circuit. Here are some key benefits and scenarios where this technique is commonly applied:

1. Power Dissipation:
Advantage: When resistors are connected in parallel, the overall power dissipation is shared between the individual resistors. This can prevent overheating or excessive power dissipation in a single resistor, especially in high-power applications.
Example: In power supplies or motor driver circuits, where large amounts of current flow through resistors, parallel resistors help distribute the heat more evenly, preventing one resistor from getting too hot and potentially burning out.
2. Improved Thermal Management:
Advantage: Distributing the current across multiple resistors can help manage heat more effectively. A single high-power resistor may have limitations on how much power it can dissipate before it reaches unsafe temperatures. By using parallel resistors, the heat is spread out, improving overall thermal performance.
Example: In high-power resistor networks used in voltage dividers or current sensing, parallel resistors allow better thermal management without the need for specialized heat sinks.
3. Availability of Components:
Advantage: It may be more practical or cost-effective to use multiple standard-value resistors than to source a single resistor with the required value, especially in cases where a precise resistance value is not readily available in a high-power rating.
Example: Sometimes a designer may need a resistor with a specific value that is not commonly available, but by combining resistors of different standard values in parallel, the desired resistance can be approximated. This can be more convenient than ordering a custom resistor.
4. Increased Power Rating:
Advantage: Multiple resistors in parallel increase the total power handling capability of the resistor network. The power rating of the parallel combination is effectively the sum of the individual power ratings of each resistor.
Example: For example, two resistors each rated for 1W in parallel can handle up to 2W of power in total, which would not be possible with a single 1W resistor.
5. Tolerance and Precision:
Advantage: In some cases, using multiple resistors can help achieve a more precise overall resistance value, especially if high tolerance resistors are used in parallel. The parallel combination may help average out the tolerance errors of individual resistors, leading to a more predictable and consistent resistance.
Example: In precision circuits, such as voltage dividers in analog signal processing, multiple resistors with tight tolerances might be combined to achieve the desired resistance value with reduced error margins.
6. Redundancy and Reliability:
Advantage: Using parallel resistors can improve the reliability of the circuit. If one resistor fails (e.g., due to overheating), the remaining resistors in the parallel configuration can continue to carry the current, which can help prevent a complete circuit failure.
Example: This is especially useful in mission-critical applications where reliability is key, such as in automotive or aerospace circuits.
Common Applications:
Power Dissipation: Power supplies, motor drivers, and high-current load resistors.
Thermal Management: Voltage dividers and high-power applications.
Precision Circuits: Applications where multiple standard resistors are used to approximate a desired resistance with minimal tolerance error.
Redundancy: Safety-critical applications where resistor failure could compromise circuit performance.
Conclusion:
Using resistors in parallel is a useful technique, especially when dealing with high power, thermal management, or component availability. It allows for better distribution of power, increased reliability, and often better thermal performance. While it might seem simpler to just use a single resistor, the flexibility, safety, and performance benefits make this approach preferable in certain scenarios.