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RESISTOR DIVIDER RULE A voltage divider referenced to Ground is created by connecting two resistors as shown in the following diagram: The output voltage ''V''out is related to ''V''in as follows: : It may be useful to note that ''R''1 and ''R''2 may each comprise many resistors in series. As a simple example, if ''R''1 = ''R''2 then : As a more specific and/or practical example, if ''V''out=6V and ''V''in=9V (both commonly used voltages), then: : and by solving using Algebra , ''R''2 must be twice the value of ''R''1. Any ratio between 0 and 1 is possible. That is, using resistors alone it is not possible to either reverse the voltage or increase ''V''out above ''V''in VOLTAGE DIVIDER AS A VOLTAGE SOURCE While voltage dividers may be used to produce very precise reference voltages, they make very poor voltage sources. This is because if a load is connected between the output voltage and ground the Effective Resistance between ''V''out and ground decreases. A change in the resistance of ''R''2 changes the load voltage, an undesirable situation for a voltage source. In terms of the above equation, if current flows into a load resistance (through ''V''out), that load resistance must be considered In Parallel with ''R''2 to determine the voltage at ''V''out. In this case, the voltage at ''V''out is calculated as follows: : |
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