Question

The op-amp and the 1 mA current source in the circuit of figure are ideal. The output of the op-amp is:

• A. -1.5 mA
• B. -1.5 V
• C. -7.5 V
• D. +1.5 V

Hint:

For ideal op-amps, remember that the output voltage will be determined by the current flowing through the feedback resistor, considering the direction of the current.

Answer 1

The Correct Option is B

In this circuit, the op-amp is configured with an ideal current source and a feedback resistor of $1.5k\Omega$. The current source provides a constant current of $1 \, \text{mA}$ through the resistor, and since the op-amp is ideal, it will maintain a virtual short between the inverting and non-inverting terminals, meaning the voltage at the inverting terminal is essentially zero.
The voltage at the output is determined by Ohm’s law: \[ V_{out} = I \times R = (1 \, \text{mA}) \times (1.5k\Omega) = 1.5 \, \text{V} \] However, since the current is flowing in the opposite direction to the voltage source, the output voltage will be negative. Therefore, the output voltage $V_{out}$ is -1.5 V.