Circuit generated noise limits analog signal processing. A measure of a circuit's ability to maintain signal integrity is given by the circuit's signal-to-noise ratio. To find this quantity we must first find the equivalent noise signal at an input generated by the circuit. This paper presents a direct and systematic method for finding the complete input equivalent noise signal through the use of the Driving Point Impedance/Signal Flow Graph methodology. With this approach a noise signal is translated unambiguously from its origin node to the input without the use of approximations or of distinctions of active device types, bipolar, MOS, or other, limited only by the device models used.