8051 interfacing context: Current-output DACs and some sensors provide an analog output as a current, which must be converted into a usable voltage for the 8051’s ADC/input stages. Is it valid to perform this current-to-voltage (I/V) conversion with a general-purpose operational amplifier configured as a transimpedance amplifier (for example, a classic 741/LM358-class op amp)?

Introduction / Context:
In many embedded systems built around the 8051 microcontroller, sensors or DACs may present their analog signal as a current rather than a voltage. Since microcontrollers and most ADC inputs expect a voltage referenced to ground, a precise current-to-voltage (I/V) conversion stage is required. The standard way to achieve this is with an operational amplifier configured as a transimpedance amplifier. This item checks whether such an op-amp solution is valid in principle for generating a usable voltage from a current-output source.

Given Data / Assumptions:

• An analog signal is available as a current source (for example, from a current-output DAC or a photodiode).
• The 8051 or its companion ADC needs a stable voltage signal within a defined input range.
• Op-amps can be used in feedback configurations to perform linear conversions.
• Proper supply rails, stability compensation, and bandwidth are available for the target op-amp.

Concept / Approach:
In a transimpedance configuration, the op-amp holds its inverting input at virtual ground and routes the input current through a feedback resistor Rf. The resulting output voltage is Vout = −Iin * Rf (sign depends on input polarity and topology). With appropriate Rf selection, the design scales the current into a voltage that fits the ADC range, while the op-amp provides low input impedance and isolation from loading effects.

Step-by-Step Solution:

Verification / Alternative check:
Simulate or prototype: inject a known current (for example from a precision source or DAC), measure Vout, and verify linearity (Vout vs. Iin). Confirm the ADC reading corresponds to expected voltages across the full scale.

Why Other Options Are Wrong:

Common Pitfalls:
Ignoring op-amp bandwidth and stability with capacitive sources, selecting Rf that saturates the output, or failing to provide appropriate reference and filtering. Always consider noise and bias currents for precision applications.

Final Answer:
Correct