Textbook on spectral and convolution methods with emphasis on circuits. Includes Fourier series, transform and Laplace transform. Periodic and semi-periodic signals; causal complex exponentials; sigma selection criterion; partial fractions; 3D plots of complex transfer functions with no poles, finite poles and infinite poles; contour integration; exotic periodic functions; numerical convolution; two faces of convolution; convolution order; convolution and pattern matching; convolution and periodic functions; reverse engineering convolution; synthesis of delta function; analysis of delta function in frequency domain; DC limit of transfer functions; partial fraction expansion involving infinite number of poles; causal periodic delta function and apparent spectrum contradiction; non-linear model linearization and small signal model; small signal model and basic MOSFET circuits; MOSFET small signal model in the frequency domain; Inverse small signal modeling.