The step response describes the result if the input to a system is the step function, i.e.: Then we have:
where only the first term is a forced pole, and the rest are the natural poles of . Additionally, since we know that the transfer function , the impulse response:
where is continuous. What this means is that we can find the impulse response of a circuit by applying as an input, then differentiating its output. These relations are summarised below: