On the stability of an LTI circuit

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SUMMARY

An LTI (Linear Time-Invariant) circuit composed of resistors, capacitors, and inductors is inherently stable, as its impulse response decays over time. The stability is mathematically represented by the transfer function having poles located in the left-half side of the complex plane, indicating negative real parts of the denominator polynomial's roots. The Routh-Hurwitz stability criterion is a key tool for analyzing this stability, ensuring that the system does not exhibit divergent behavior or continuous oscillations. Kirchhoff's Laws play a crucial role in maintaining this stability by governing energy conservation within the circuit.

PREREQUISITES
  • Understanding of Linear Time-Invariant (LTI) systems
  • Familiarity with transfer functions and poles in the complex plane
  • Knowledge of the Routh-Hurwitz stability criterion
  • Basic principles of Kirchhoff's Laws
NEXT STEPS
  • Study the implications of the Routh-Hurwitz stability criterion in various LTI circuit designs
  • Explore the mathematical derivation of transfer functions for different LTI circuits
  • Investigate the role of Kirchhoff's Laws in energy conservation within electrical circuits
  • Learn about alternative stability analysis methods, such as Nyquist and Bode plots
USEFUL FOR

Electrical engineers, circuit designers, and students studying control systems or circuit analysis will benefit from this discussion on LTI circuit stability.

mjtsquared
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An LTI circuit such as one composed of resistors, capacitors, and inductors, in general is a stable LTI system, i.e. its impulse response is one that decays over time. I have no problem with that, as it speaks for itself through laws of energy conservation, but I want to see this from a mathematical standpoint.

Following from this assumption, the transfer function of the system must have poles on the left-half side of the complex plane i.e. the real parts of the potentially complex roots of the denominator polynomial are negative. I know about the Routh-Hurwitz stability criterion, and have used it on many examples which do pass the criterion, but I still can't find any generality. If it's something that always allows this to happen, it must be something with Kirchhoff's Laws. What do you think?

Good day!
 
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If an impulse was fed in and the energy in the system grew exponentially without bound, that would be generating energy from nothing. That rules out divergent behavior. Also, any resistance at all would bleed off energy. That rules out a stable continuous oscillation.
 

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