Voltage DividerPublished on 24/2/2012 & updated on 3/8/2018
Circuit of Voltage DividerAs we mentioned above, two series resistors and voltage source constitutes a simple voltage divider. This circuit can be formed in several ways as shown below.
In the above figure, (A) represents shorthand, (B) represents longhand and (C) and (D) shows the resistors in different and same angle respectively.
But all the four circuits are in effect the same. R1 is the resistor which is always close to the input voltage source and R2 is the resistor which is near to the ground. Vout is the voltage drop across the resistor, R2. It is actually the divider voltage which we get from this circuit as the output.
Equation of Voltage Divider in Unloaded ConditionThe simple voltage divider circuit with reference to ground is shown in the figure below. Here, two electrical impedances (Z1 and Z2) or any passive components are connected in series. The impedances may be of resistors or inductors or capacitors. The output of the circuit is taken across the impedance, Z2.
Under open circuit output condition; that is there will be no current flow in the output side, then Now we can prove the output voltage equation (1) using the basic law, Ohm’s Law
Substitute equation (4) in (3), we get So, the equation is proved. The transfer function of the above equation is This equation is also called as Divider’s The capacitive divider circuits never allow DC input to pass. They work on AC input. For Inductive divider with non-interacting inductors, the equation becomes The inductive divider divides the DC input analogous to resistor divider circuit depending on resistance and it divides AC input with regard to the inductance. A basic Low-pass RC filter circuit is shown below which comprises of a resistor and capacitor. C → Capacitance R → Resistance XC → Reactance of the capacitor ω → Radiant frequency j → Imaginary unit Here, the divider’s voltage ratio is RC → Time constant of the circuit represented as τ.
Voltage Divider Under Loaded ConditionNow, we can see the voltage divider circuit in loaded condition. Here, the resistors (R1 and R2) are taken for simplicity. A resistor (RL) is connected across the output. Then the equation becomes, R2 and RL are parallel to each other. The circuit with loaded condition is shown below.
Applications of Voltage DividerApplications include Logic level shifting, Sensor measurement, High voltage measurement, Signal Level Adjustment. The measuring instruments such as Multimeter and Wheatstone bridge consist of voltage divider. Resistor voltage divider is usually used to generate reference voltages or for decreasing the magnitude of the voltage for the ease of measurement. In addition to this; at low frequency, it can be function as signal attenuators. In the case of DC and very low frequencies, the resistor voltage divider is suitable. Capacitive voltage divider is implemented in power transmission for high voltage measurement and to compensate load Capacitance.
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