Amplifier Gain Stability - Part II — Lesson 4

This lesson covers the concept of stability in amplifier. It delves into the conditions for unconditional stability and potential instability, explaining the role of gamma in determining stability. The lesson further explores the concept of stability circles, including input and output stability circles, and how they can be used to identify stable and potentially unstable regions. It also discusses the impact of frequency on stability and the importance of stability in amplifier design. For instance, if an amplifier is not stable, the gain achieved will not be sustainable.

Video Highlights

00:15 - Even and odd mode characteristic impedance
01:41 - Boundary between unconditional stability and potential instability.
04:08 - Concept of output and input stability circles.
07:56 - Conditions for stability based on the modulus of S11.
14:59 - Introduction to the concept of input and output stability circles with respect to frequency
23:55 - Summary

Key Takeaways

- Stability in microwave integrated circuits is determined by the conditions of gamma. If the modulus of gamma is less than 1, the circuit is stable.
- Stability circles, including input and output stability circles, are used to identify stable and potentially unstable regions.
- The position of stability circles can shift based on the frequency, impacting the stability of the circuit.
- Amplifier design requires careful consideration of stability. Without stability, the gain achieved will not be sustainable.
- Stability design does not provide unique values of gamma, allowing for flexibility in choosing values that provide the correct gain and noise.