The Circuit Designer's Companion, 2nd Edition

114 The Circuit Designer’s Companion

delivered units, in order to have room for manoeuvre when a given batch shows a high

value.

The consequence of this is that if your design is sensitive to leakage current then the

prototype may work well while a production model does not. The probability is high

that a device selected at random for the prototype will have a low leakage, whereas

some production devices will come from high-leakage batches. If the design proceeded

on the basis only of satisfactory measurements on the prototype then the seeds have

been sown for production difficulties. To avoid them, always work on worst-case

calculations even though ...