Op-Amp Review Flashcards
What is the differential op-amp equation?
Vout = A(V+ - V-)
What are the ideal op-amp properties?
> Infinite open-loop gain (A)
> Infinite input impedance
> Zero output impedance
> Virtual ground principle
What are the practical op-amp properties?
> Very high open-loop gain (A)
> Very high input impedance
> Very low output impedance (>100Ω)
> Virtual ground principle
> Limited current of only a few mA
What is negative feedback?
> It is a method of circuit design
> Negative feedback is used for useful amplifier circuits to limit the open-loop gain (A). This limited gain is called the closed-loop gain (G)
What is the open-loop gain?
> This is the large (unlimited) gain that an op-amp has without any feedback circuit tropology
> Ideally it is infinite but in actual fact it is just very large
What is the closed-loop gain?
> This is the actual gain of the op-amp that is limited to a fixed amount due to negative feedback.
What is the circuit diagram for a non-inverting amplifier?
What is the full gain equation of a non-inverting amplifier?
Vout / Vin = A / ( 1 + A ( R1 / ( R1 + R2 ) ) )
Derive the non-inverting amplifier equation
What is the condensed gain equation for a non-inverting amplifier?
G = A / ( 1 + AB )
How can the gain equation for a non-inverting amplifier be simplified?
G ≈ 1 / B ≈ 1 + R2 / R1
What is the range of the gain of a non-inverting op-amp?
G > 1 Cannot be lower than unity; as seen by the equation: G ≈ 1 + R2 / R1
What is the input and output impedance of a non-inverting op-amp?
Input: The impedance of the op-amp (very high)
Output: R1 + R2
What are the advantages and disadvantages of a non-inverting op-amp?
Advantages:
> Higher input impedance
> Output is not inverted
Disadvantages:
> Can’t have a closed loop gain < 1
> Input voltages may not be near ground due to common-mode input limit
What is the circuit diagram for an inverting amplifier?
Derive the inverting amplifier gain equation
