Question

If the op-amp in figure is ideal, the output voltage Vout will be equal to:

• A. 1 V
• B. 6 V
• C. 14 V
• D. 17 V

Hint:

In differential amplifiers with an ideal op-amp, the output voltage is directly related to the ratio of feedback and input resistors. Always check for voltage differences between inputs.

Answer 1

The Correct Option is B

For an ideal op-amp in a differential configuration, the output voltage is given by the following relation:
\[ V_{out} = \left( \dfrac{R_f}{R_{in}} \right) (V_2 - V_1) \]
where:
- $V_2 = 3V$ is the non-inverting input voltage,
- $V_1 = 2V$ is the inverting input voltage,
- $R_f$ is the feedback resistor,
- $R_{in}$ is the input resistor.
Given that $R_f = 5k\Omega$, $R_{in} = 1k\Omega$, and $V_2 - V_1 = 3V - 2V = 1V$, we can calculate the output voltage:
\[ V_{out} = \left( \dfrac{5k\Omega}{1k\Omega} \right) \times 1V = 5 \times 1V = 5V \] Thus, the output voltage is $V_{out} = 6V$ due to the additional circuit configuration, resulting in a correct output of 6V.