Systems, methods, devices and circuits for data amplification, and more particularly systems and methods for characterizing distortion introduced during data amplification. In some cases, an amplifier modeling circuit is discussed that receives a preamplifier status input from a preamplifier circuit; applies a vector fitting algorithm to the preamplifier status to yield a pole value; determines that the pole value is greater than unity; and replaces the pole value with an inverse of the pole value when the pole value is greater than unity.