Potential divider

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• Potential divider

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Basic circuit

• Simple series circuit
• Uniform current flow
• Two equal resistors
• Voltage drop across each is the same

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Circuit orientation

• Rotate and reflect

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Split the cell

• Open-out the cell

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Introduce supply rails

• Change to supply rail representation
• Supply rail Vss
• Ground rail 0V
• Label resistors
• Label voltmeters

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Introduce the output voltage

• Add the output voltage
• Vout
• but this is still the same circuit
• Both resistors are equal
• Both voltages are equal
• Output voltage is the same as the voltage across
  Rb I.e. Vb

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Principle of operation

• Change the value of Rb
• Relative to Ra
• Changes the Vout
• Qualitatively
• Rb big Vout big
• Rb small Vout small

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Calculations

• Current is the same through both resistors

I
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Example

• The voltage will be divided in the same ratio as
  the resistors

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Applications

• Replace one of the fixed resistors with a
• Variable resistor
• Variable output voltage
• Volume control
• Sensor
• Thermistor
• LDR
• Electronic input device
• Physical quantity to electrical signal

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