If the input resistor of an inverting amplifier using OP-AMP is doubled and the feedback resistor remains the same, what happens to the magnitude of voltage gain?
It is halved
An inverting amplifier using an operational amplifier (OP-AMP) has a configuration where the voltage gain \(A_v\) is determined by the feedback resistor (\(R_f\)) and the input resistor (\(R_{in}\)). The formula for the voltage gain of an inverting amplifier is given by:
\(A_v = -\dfrac{R_f}{R_{in}}\)
Let's analyze what happens when the input resistor \(R_{in}\) is doubled, while the feedback resistor \(R_f\) remains unchanged.
- Initially, the voltage gain is:
\(A_v = -\dfrac{R_f}{R_{in}}\)
- If \(R_{in}\) is doubled, we have a new input resistor value of \(2R_{in}\). The modified voltage gain becomes:
\(A_v' = -\dfrac{R_f}{2R_{in}}\)
- Comparing the new gain \(A_v'\) with the original gain \(A_v\):
The ratio of the new gain to the original gain is:
\(\dfrac{A_v'}{A_v} = \dfrac{-\dfrac{R_f}{2R_{in}}}{-\dfrac{R_f}{R_{in}}} = \dfrac{1}{2}\)
This indicates that the new gain is half the original gain.
Therefore, when the input resistor of an inverting amplifier is doubled, the magnitude of the voltage gain is halved. Hence, the correct answer is: It is halved.
Similar Questions
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In an operational amplifier integrator circuit, which component acts as feedback between the output and the input?
To convert an op-amp integrator into a practical integrator (avoiding low-frequency saturation), which component is typically added in parallel with the feedback capacitor?
When analyzing a closed-loop circuit containing an ideal operational amplifier, what assumption must be applied regarding the currents entering the inverting and non-inverting input pins?
What happens to the gain of a non-inverting amplifier using OP-AMP if the feedback resistor value is increased by 5 % while keeping the input resistor constant? (Assuming the OP-AMP remains in linear range for operation.)
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