How does the load connected to a voltage divider resistor affect its output?

Hey there! As a supplier of voltage divider resistors, I've been getting a lot of questions lately about how the load connected to a voltage divider resistor affects its output. So, I thought I'd write this blog post to break it down for you in a way that's easy to understand.

First off, let's quickly go over what a voltage divider resistor is. A voltage divider is a simple circuit made up of two or more resistors connected in series. The purpose of a voltage divider is to divide a larger input voltage into a smaller output voltage. The output voltage is determined by the ratio of the resistances in the circuit.

Now, when we talk about the load connected to a voltage divider resistor, we're referring to any device or component that draws current from the output of the voltage divider. This could be a sensor, a microcontroller, or any other electrical device. The load can have a significant impact on the output voltage of the voltage divider, and here's why.

The Ideal Voltage Divider

In an ideal world, a voltage divider would work perfectly regardless of the load connected to it. The output voltage would be solely determined by the ratio of the resistances in the circuit. For example, if we have a voltage divider with two resistors, R1 and R2, connected in series across an input voltage Vin, the output voltage Vout can be calculated using the following formula:

Vout = Vin * (R2 / (R1 + R2))

This formula assumes that there is no current flowing through the load connected to the output of the voltage divider. In other words, the load has an infinite resistance. In this case, the voltage divider works exactly as expected, and the output voltage is a fraction of the input voltage determined by the resistance ratio.

The Real World: Load Effects

However, in the real world, no load has an infinite resistance. All loads draw some amount of current, and this current can affect the operation of the voltage divider. When a load is connected to the output of a voltage divider, it effectively creates a parallel circuit with one of the resistors in the voltage divider. This changes the overall resistance of the circuit and, consequently, the output voltage.

Let's take a closer look at how this works. Suppose we have the same voltage divider circuit with R1 and R2, and we connect a load resistor RL in parallel with R2. The equivalent resistance of R2 and RL in parallel, which we'll call Req, can be calculated using the following formula:

1 / Req = 1 / R2 + 1 / RL

Req = (R2 * RL) / (R2 + RL)

Now, the output voltage of the voltage divider can be calculated using the same formula as before, but with Req replacing R2:

Vout = Vin * (Req / (R1 + Req))

As you can see, the output voltage is now dependent on the value of the load resistor RL. If RL is very large compared to R2, then Req will be approximately equal to R2, and the output voltage will be close to the ideal value calculated without considering the load. However, if RL is small compared to R2, then Req will be significantly smaller than R2, and the output voltage will be lower than the ideal value.

Examples of Load Effects

To illustrate the impact of the load on the output voltage of a voltage divider, let's consider a few examples.

Example 1: High Load Resistance
Suppose we have a voltage divider with R1 = 10 kΩ and R2 = 10 kΩ, connected across an input voltage of Vin = 10 V. The ideal output voltage, without considering the load, would be:

Vout = Vin * (R2 / (R1 + R2)) = 10 V * (10 kΩ / (10 kΩ + 10 kΩ)) = 5 V

Now, let's connect a load resistor RL = 100 kΩ in parallel with R2. The equivalent resistance of R2 and RL in parallel is:

Req = (R2 * RL) / (R2 + RL) = (10 kΩ * 100 kΩ) / (10 kΩ + 100 kΩ) ≈ 9.09 kΩ

The new output voltage is:

Vout = Vin * (Req / (R1 + Req)) = 10 V * (9.09 kΩ / (10 kΩ + 9.09 kΩ)) ≈ 4.76 V

As you can see, the output voltage has decreased slightly due to the load, but it's still close to the ideal value.

Example 2: Low Load Resistance
Now, let's consider the same voltage divider circuit, but this time we'll connect a load resistor RL = 1 kΩ in parallel with R2. The equivalent resistance of R2 and RL in parallel is:

Req = (R2 * RL) / (R2 + RL) = (10 kΩ * 1 kΩ) / (10 kΩ + 1 kΩ) ≈ 0.91 kΩ

The new output voltage is:

Vout = Vin * (Req / (R1 + Req)) = 10 V * (0.91 kΩ / (10 kΩ + 0.91 kΩ)) ≈ 0.83 V

In this case, the output voltage has decreased significantly due to the load, and it's much lower than the ideal value.

Choosing the Right Resistors

So, how do we choose the right resistors for a voltage divider to minimize the effects of the load? The key is to make sure that the resistances in the voltage divider are much larger than the load resistance. This way, the current drawn by the load will have a minimal impact on the operation of the voltage divider.

For example, if we know that the load resistance will be in the range of a few kilohms, we might choose resistors in the voltage divider that are in the range of hundreds of kilohms or even megohms. This will ensure that the equivalent resistance of the voltage divider remains relatively constant, even when the load is connected.

Our Voltage Divider Resistors

At our company, we offer a wide range of voltage divider resistors to meet your specific needs. Whether you're looking for a High Power Precision High-voltage Divider Resistor, a Precision High-voltage Voltage Divider Resistor, or a High Voltage Divider Resistor, we've got you covered.

Our resistors are designed with high precision and stability, ensuring accurate voltage division even in the presence of a load. We use high-quality materials and advanced manufacturing techniques to produce resistors that offer excellent performance and reliability.

Conclusion

In conclusion, the load connected to a voltage divider resistor can have a significant impact on its output voltage. When a load is connected, it effectively changes the overall resistance of the circuit, which can cause the output voltage to deviate from the ideal value. To minimize the effects of the load, it's important to choose resistors in the voltage divider that are much larger than the load resistance.

If you're in the market for voltage divider resistors, we'd love to hear from you. Our team of experts is ready to help you choose the right resistors for your application and answer any questions you may have. So, don't hesitate to reach out and start a conversation about your voltage divider resistor needs.

References

• Boylestad, R. L., & Nashelsky, L. (2012). Electronic Devices and Circuit Theory. Pearson.
• Sedra, A. S., & Smith, K. C. (2015). Microelectronic Circuits. Oxford University Press.