This lecture covers the small signal analysis of a differential amplifier, focusing on differential gain and common mode gain. The instructor explains the concept of small signal diagrams and how to analyze the differential gain using the half-circuit method. The lecture also delves into the common mode gain and rejection rate, highlighting the importance of symmetrical circuit design. Various small final signal patterns are presented to illustrate the theoretical concepts discussed. The slides provide detailed equations and diagrams to aid in understanding the analysis of differential and common mode gains in MOSFET amplifiers.