13.3.3 Understanding feedback and stability

• Negative feedback stabilizes the operation of an op-amp and reduces sensitivity to component variations.

  True
• Match the stability parameters with their definitions:

  Gain Margin (GM) ↔️ Gain added before instability

  Phase Margin (PM) ↔️ Phase lag before instability
• An op-amp with a gain margin of 10 dB and a phase margin of 45 degrees is considered stable
• An op-amp with a GM of 10 dB and a PM of 45 degrees is stable.


  True
• Negative feedback stabilizes op-amp operation and reduces sensitivity to component variations.


  True
• Negative feedback is commonly used in op-amp circuits to improve stability and linearity.

  True
• Positive feedback is preferred in high-performance amplifier designs.

  False
• Match the type of feedback with its effect on stability:

  Positive Feedback ↔️ Instability

  Negative Feedback ↔️ Stability
• Positive feedback in op-amps is achieved when the output signal is fed back in phase with the input.


  True
• Negative feedback in op-amps feeds the output signal out of phase
• Common instability issues in op-amps with feedback:

  1️⃣ Positive Feedback

  2️⃣ Parasitic Capacitances

  3️⃣ Bandwidth Limitations
• Match the instability mitigation technique with its description:

  Negative Feedback ↔️ Improves stability and linearity

  Compensation Capacitors ↔️ Compensate for parasitic capacitances

  Frequency Compensation ↔️ Introduces additional poles and zeros

  Gain Reduction ↔️ Reduces overall gain for stability
• Positive feedback occurs when the output signal is fed back in phase
• Negative feedback improves both the stability and the linearity
• What is the stability criterion for phase margin (PM) in degrees?

  PM > 0 degrees
• The Phase Margin (PM) measures the amount of phase lag before instability occurs and must be greater than 0
• Match the type of feedback with its effect on stability:

  Positive Feedback ↔️ Instability

  Negative Feedback ↔️ Stability
• Positive feedback can lead to oscillations due to reduced stability and linearity
• Negative feedback in op-amps improves both stability and linearity
• The Gain Margin (GM) must be greater than 0 dB for the op-amp to be stable
• What are the two main types of feedback in operational amplifiers (op-amps)?

  Positive and negative
• Match the type of feedback with its effect on stability:

  Positive Feedback ↔️ Reduces stability

  Negative Feedback ↔️ Improves stability
• In a non-inverting amplifier, where is the output signal fed back to create negative feedback?

  Negative terminal
• Bandwidth limitations in op-amps can lead to instability at higher frequencies.

  True
• What is the primary goal of applying instability mitigation techniques in op-amp circuits?

  Ensure stable operation
• What does feedback refer to in operational amplifiers?

  Routing output back to input
• In which type of feedback is the gain increased dramatically, potentially leading to instability?

  Positive feedback
• A gain margin greater than 0 dB indicates stability in an op-amp.


  True
• What is the definition of Gain Margin (GM) in op-amp stability criteria?

  Gain added before instability
• Positive feedback in op-amps feeds back the output signal in phase
• What effect does negative feedback have on the gain of an op-amp?

  Decreases the gain
• How does positive feedback affect the stability of an op-amp?

  Reduces stability
• What does the Nyquist Stability Criterion assess in op-amps?

  Encircling the critical point
• Negative feedback improves both the stability and linearity of op-amps.


  True
• Positive feedback in op-amps increases the gain dramatically but can lead to instability
• Negative feedback reduces the gain of an op-amp but improves its stability and linearity.


  True
• Parasitic capacitances in op-amps can introduce phase shifts that destabilize the feedback loop
• Adding compensation capacitors in parallel with feedback resistors helps to compensate for parasitic capacitances.