Feedback Theory

Mastering negative and positive feedback for stable, predictable circuit behavior.

Feedback is fundamental to analog design. Negative feedback trades gain for stability and linearity, while positive feedback enables oscillators and comparators. Understanding feedback is essential for amplifier design.

Objectives

  • Distinguish negative and positive feedback
  • Calculate closed-loop gain from open-loop gain and feedback factor
  • Analyze feedback effects on bandwidth, impedance, and distortion
  • Understand stability and phase margin
  • Design compensation networks for stable operation

Key Takeaways

  • Negative feedback reduces and stabilizes gain
  • Closed-loop gain ≈ 1/β when loop gain is high
  • Phase margin determines stability
  • Compensation ensures stable operation with feedback