Question

The output \( V_o \) of the ideal OpAmp used in the circuit shown below is 5 V. Then the value of resistor \( R_L \)in kilo ohm (kΩ) is:

• A. 2.5
• B. 5
• C. 25
• D. 50

Hint:

For OpAmp circuits with feedback, use the concept of virtual short and voltage divider rule to analyze the behavior of the circuit.

Answer 1

The Correct Option is C

We are given an ideal OpAmp circuit with the output \( V_o = 5 \) V, and we need to determine the value of the resistor \( R_L \) in kilo ohms.

Step 1: Understand the circuit.
The OpAmp circuit consists of resistors with equal values of \( 10 \, \text{k}\Omega \) at various points. The circuit uses negative feedback, and for an ideal OpAmp, the voltage at the inverting and non-inverting inputs are equal.

Step 2: Apply the virtual short concept.
For an ideal OpAmp, the voltage at both inputs must be the same. Therefore, the voltage at the inverting terminal is also \( 1 \, \text{V} \) (the voltage at the non-inverting terminal).

Step 3: Use the voltage divider rule.
We can apply the voltage divider rule to find \( R_L \) from the given output voltage. Using Ohm's law and solving for \( R_L \), we find that \( R_L = 25 \, \text{k}\Omega \).

Final Answer: 25.