Electronics

Step 1: Analyze an ideal Zener regulator circuit. A simple Zener regulator consists of a series resistor ( ) connected to an input voltage ( ), and a Zener diode in parallel with the load resistor ( ). The purpose of the Zener diode is to maintain a constant voltage ( ) across the load.
Step 2: Determine the series current ( ). The series current flows through the series resistor . The voltage across is the difference between the input voltage and the Zener voltage: . According to Ohm's law, the series current is:
Step 3: Evaluate the effect of a change in load resistance. Assuming the regulator is operating correctly, the Zener diode maintains at a constant value. The input voltage and the series resistance are also constant. Since all the terms on the right side of the equation for are constant, the series current remains constant.
Step 4: Consider the current distribution. The series current splits into the Zener current ( ) and the load current ( ): . If the load resistance decreases, the load current increases. Since is constant, the Zener current must decrease to compensate. The regulator works as long as remains positive.

Step 1: Understand the function of a controlled current source. A controlled current source is an electronic circuit that delivers a constant current to a load, where the value of this current is set by an input signal.
Step 2: Analyze the role of the Op-Amp in this application. In a typical Op-Amp based controlled current source (like a Howland current pump or a simple transistor-based design), an input voltage ( ) is applied to one of the Op-Amp's inputs. The Op-Amp uses its high gain and feedback to adjust its output in such a way that the current flowing through the load ( ) becomes directly proportional to the input voltage ( ).
Step 3: Classify the circuit based on its input and output signals. The circuit takes a voltage as its input signal and produces a proportional current as its output signal. This is the definition of a voltage-to-current converter. Another name for this type of circuit is a transconductance amplifier.

Step 1: Analyze the characteristics of each BJT configuration. - A. Common Base (CB): This configuration has a low input impedance and high output impedance. Its current gain ( ) is slightly less than 1. However, it can have a very high voltage gain. Therefore, it provides "Voltage Gain but no Current Gain" (since the gain is less than unity). This matches II. - B. Common Emitter (CE): This is the most widely used configuration. It has a medium input and output impedance. It provides significant gain for both current ( ) and voltage. Therefore, it provides "Both Current and Voltage Gain". This matches III. - C. Common Collector (CC): Also known as an emitter follower, this configuration has a high input impedance and low output impedance. Its voltage gain is approximately 1 (unity). It has a high current gain ( ). Therefore, it provides "Current Gain but no Voltage Gain". This matches I.
Step 2: Formulate the correct matching sequence. Based on the analysis: - A II - B III - C I This sequence corresponds to option (2).

Concept: A NAND gate is a digital logic gate that performs the NOT operation on the output of an AND gate.
Step 1: Write the AND gate expression.} For two inputs and ,
Step 2: Apply the NOT operation.} Taking the complement of the AND output,
Step 3: Interpretation.} The output of a NAND gate becomes only when both inputs are . In all other cases, the output is . Thus, the Boolean expression of a two-input NAND gate is

Concept: A p-n junction diode contains a depletion region near the junction where mobile charge carriers are absent. This region forms due to recombination of electrons and holes.
Step 1: Effect of reverse bias.} In reverse bias, the positive terminal of the battery is connected to the n-side and the negative terminal to the p-side. This pulls electrons and holes away from the junction.
Step 2: Resulting change in depletion region.} Since carriers move away from the junction, the depletion region expands and the potential barrier increases.
Step 3: Conclusion.} Therefore, under reverse bias, the width of the depletion layer increases.