JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELECTRONIC CIRCUIT ANALYSIS Previous Question Paper (April/May - 2023 - R15)

Cascading transistor amplifiers offers several benefits:

• Increased Gain: Each stage amplifies the signal, so the overall voltage or current gain is the product of the individual stage gains, leading to a much higher overall amplification.
• Improved Input/Output Impedance: By selecting appropriate amplifier configurations for each stage (e.g., common emitter followed by common collector), the input and output impedance characteristics can be tailored to match source and load impedances, maximizing power transfer.
• Bandwidth Extension (in some configurations): While cascading generally reduces bandwidth, specific configurations can be used to achieve a wider overall bandwidth than a single stage might provide.

Miller's Theorem: Miller's theorem is a technique used to simplify the analysis of circuits containing a component with a finite impedance connected between a node and a feedback path (typically to the input node). It states that a two-terminal component with impedance Z connected between a node with voltage V1 and a node with voltage V2 can be replaced by two separate impedances connected from each node to a common reference (ground). If the feedback path is from V2 to V1, the impedance Z can be replaced by an impedance Z/(1-A_v) from V1 to ground and Z/(1-1/A_v) from V2 to ground, where A_v = V2/V1 is the voltage gain between the two nodes.

Duality of Miller's Theorem: The dual of Miller's theorem applies to components connected between a node and a feedback path, but instead of voltage feedback, it involves current feedback. It simplifies the analysis of circuits with components connected between two nodes where the current through the component is proportional to the voltage difference between them. For a component with admittance Y connected between node 1 and node 2, where the current from node 2 to node 1 is I_f = k * (V2 - V1), it can be replaced by two admittances connected to ground. If the feedback is from node 2 to node 1, the admittance Y can be replaced by Y(1-k) from node 1 to ground and Y(1-1/k) from node 2 to ground.