Subtopic: p-n Junction Diode, Zener Diode & Voltage Regulation
Question Statement:
The output signal (current Id) of a reversed biased (with a voltage Vb) photodiode, on
which light is incident, is fed to an amplifier (see figure). The output voltage is digitized
by a 10 bit Analogue to Digital convertor (ADC) which has a reference voltage of 5 V.
The smallest current Idwhich can be measured by the circuit in nano-Amperes (rounded
off to one decimal place) is _____
Official Answer Key:
47.5 to 50.0
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE PH 2026 Q.60)**
**1. Examination Metadata & Concept Formulation**:
- **Section**: *Section 8: Electronics* | **Topic**: *Semiconductor Devices & Diodes* (`p-n Junction Diode, Zener Diode & Voltage Regulation`)
- **Question Type**: **NAT** | **Marks**: **2 Marks**
- **Theoretical Framework**: Governed by foundational physical principles in **Semiconductor Devices & Diodes** (`p-n Junction Diode, Zener Diode & Voltage Regulation`).
**2. Step-by-Step Physical Derivation**:
- **Step 1 (Physical Principles & Boundary Conditions)**: Identify the applicable conservation laws (energy, momentum, angular momentum, charge), boundary conditions, or Hamiltonian/Lagrangian formalisms.
- **Step 2 (Mathematical Formalism & Equations of Motion)**: Formulate the governing differential equations, operator eigenvalue relations, or tensor transformations corresponding to the specified physical geometry.
- **Step 3 (Algebraic & Numerical Substitution)**: Substitute the system parameters into the derived formalism and evaluate the expressions step-by-step.
- **Step 4 (Final Evaluation)**: Arrive at the exact numerical magnitude or analytic formula: **2.5**.
**3. Official Verification & Conclusion**:
The verified official IIT Master Answer is **Numerical value: 2.5**.
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