Exam Question

This question assesses the understanding of a basic amplifier model and the effects of applying negative series voltage feedback. The solution is presented in two parts as requested.
### **Part 1: Amplifier without Feedback**
#### **Concept & Model**
An amplifier can be modeled by its key characteristics: input resistance ($R_{in}$), output resistance ($R_{out}$), and open-circuit voltage gain ($A_v$). The output stage is modeled as a Thévenin equivalent circuit, consisting of an ideal voltage source ($V_{out, oc}$) in series with the output resistance ($R_{out}$). The voltage of this source is dependent on the input voltage ($V_{in}$) and the gain, such that $V_{out, oc} = A_v \times V_{in}$.