Voltage Divider Rule

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Voltage Divider rule

The voltage divider rule is very simple and shows that the output voltage Vout is a fraction of the input voltage Vin, and the voltages across the resistors divide in ratio to their values.

In electronics , a voltage divider (also known as a potential divider ) is a passive linear circuit that produces an output voltage ( V out ) that is a fraction of its input voltage (V in ). Voltage division is the result of distributing the input voltage among the components of the divider. A simple example of a voltage divider is two resistors connected in
series as shown above, with the input voltage applied across the resistor
pair and the output voltage emerging from the connection
between them.

A voltage divider is a simple circuit which turns a large voltage into a smaller one. Using just two series resistors and an input voltage, we can create an output voltage that is
a fraction of the input. Voltage dividers are one of the most fundamental circuits in electronics. If learning Ohm’s law was like being introduced to the ABC’s, learning about voltage dividers would be like learning how to spell cat.

Ideal Voltage Divider

There are two important parts to the voltage divider:

1. The circuit and

2. The equation.

The Circuit

A voltage divider involves applying a voltage source across
a series of two resistors. You may see it drawn a few
different ways, but they should always essentially be the
same circuit.

Examples of voltage divider circuit are as shown below and they are basically the same.

Voltage Divider Circuits

We’ll call the resistor closest to the input voltage (Vin ) R1, and the resistor closest to ground R2 . The voltage drop across R2 is called Vout , that’s the divided voltage our circuit exists to make.

That is all there is to the circuit! Vout is our divided voltage. That is what will end up being a fraction of the input voltage.

The Equation

The voltage divider equation assumes that you know three values of the above circuit: the input voltage (V in), and both resistor values (R1 and R2 ). Given those values, we can use
this equation to find the output voltage (V out):

Voltage Divider formula

Memorize they equation!

This equation states that the output voltage is directly proportional to the input voltage and the ratio of R1 and
R2 .

If you would like to find out where this comes from, check it out on busybrained.com/?p=70 where the equation is derived. But for now, just write it down and remember it!

Resistor voltage dividers are commonly used to create reference voltages, or to reduce the magnitude of a voltage so it can be measured, and may also be used as signal attenuators at low frequencies. For direct current and relatively low frequencies, a voltage divider may be
sufficiently accurate if made only of resistors.

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