Questions and Answers
What is the name of the operational amplifier circuit configuration shown above?
What is the condition for the differential amplifier circuit to become a Unity Gain Differential Amplifier?
What is the purpose of adding more resistors in parallel with the input resistors R1 and R3?
What happens to the output voltage sum when input V1 is higher than input V2?
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What is the name of the resistive network commonly used with the differential amplifier circuit?
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What is the function of the circuit in the 'Light Activated Differential Amplifier'?
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What is the expression for the output voltage Vout when all the resistors are of the same ohmic value?
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What is the purpose of using a differential amplifier circuit?
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What is the main function of a differential amplifier?
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Why can an operational amplifier be called a differential amplifier?
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What is the primary difference between a differential amplifier and a summing amplifier?
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What happens when signals are connected to both input terminals of an operational amplifier?
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What is the purpose of using a differential amplifier?
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How many input signals can be connected to a standard operational amplifier?
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What type of circuit is a differential amplifier?
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What is the output voltage of a differential amplifier proportional to?
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Study Notes
The Differential Amplifier
- Amplifies the voltage difference between the inverting and non-inverting inputs
- A voltage subtractor circuit that produces an output voltage proportional to the voltage difference of two input signals
- Can be used to amplify a single input signal with the other input connected to ground
Operation
- Can connect signals to both inverting and non-inverting inputs at the same time
- Output voltage is proportional to the difference between the two input voltage signals (V1 and V2)
- Acts as a Subtractor, unlike a summing amplifier which adds or sums together the input voltages
Differential Amplifier Circuit
- Shown below: 
- Can use superposition to solve for the output voltage Vout
Transfer Function
- Given as: Vout = (R3/R1)(V2 - V1) + (R4/R2)(V2 - V1)
- Can be simplified to: Vout = (R/R)(V2 - V1) when R1 = R2 and R3 = R4
- Becomes a Unity Gain Differential Amplifier when R1 = R2 = R3 = R4, with a voltage gain of exactly one or unity
- Output expression: Vout = V2 – V1
- Output voltage sum is negative if V1 > V2, and positive if V2 > V1
Applications
- Can be made to "Add" or "Subtract" voltages applied to their respective inputs by adding more resistors in parallel with the input resistors R1 and R3
- Can be used with a "Resistive Bridge" (Wheatstone Bridge) to create a differential voltage comparator
- Can be used with sensors like thermistors or light-dependent resistors to detect changes in temperature or light  
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Description
This quiz covers the concepts of differential amplifiers, voltage subtraction and output voltage in electronics. Test your knowledge on the differential amplifier circuit and its applications.
