The dominant source of self-noise in a sensor system is often assumed to be the first-stage preamplifier. While this can be a poor assumption especially for new-technology sensors, the relationship between the transducer and its electronics is a critical one to consider in the design process. A poor choice for the electronics can negate any potential gains in noise performance from the transducer. This paper explores the inter-relationships between the transducer and its electronics for the important varieties of receiving transducers whether those transducers are simple, self-generating transducers, or complex, feedback-controlled, ac-biased transducers. While this paper will approach the problem from fundamentals, the common figures-of-merit will also be examined and their limitations noted. A number of design guidelines and comparison charts will be presented to facilitate identification of the dominant noise source early in the design process and to permit rough estimation of the achievable noise performance of a particular sensor configuration.