Question

An OPAMP is connected in a circuit with a Zener diode as shown in the figure. The value of resistance \( R \) in \( \Omega \) for obtaining a regulated output \( V_0 = 9 \, \text{V} \) is: 

Hint:

For OPAMP circuits with Zener diodes, use the voltage divider rule to relate input and output voltages.

Answer 1

Step 1: Understand the OPAMP circuit.
In this OPAMP circuit, the Zener diode is used to regulate the output voltage to 9 V. The voltage across the Zener diode is \( V_Z = 4.7 \, \text{V} \). The OPAMP will adjust the output to maintain the required voltage.
Step 2: Apply the voltage divider rule.
The output voltage \( V_0 \) is determined by the voltage divider: \[ V_0 = V_{\text{in}} \times \frac{R}{R + R_2} \] Substitute the known values and solve for \( R \).
Step 3: Conclusion.
The required value of \( R \) is approximately 5.1 \( \text{k}\Omega \).