Analog circuit analysis begins by expanding nonlinear transistor characteristics around a bias point. For a device current $i(v)$, the small-signal conductance is $g = \left.\frac{di}{dv}\right|_{Q}$, and the resulting linear model governs gain, input/output impedance, and bandwidth near the operating point.

Negative feedback improves accuracy and desensitizes circuits to parameter variation, but it can also destabilize systems when phase lag reduces the margin. Stability is commonly studied using loop gain, Nyquist criteria, and Bode plots, with compensation networks deliberately shaping poles and zeros.