6.1 Introduction

So far we have covered some of the theoretical basics involved in making good optical laboratory measurements and in the electronic circuitry needed. We know a little about sources and detectors, their noise, and the added noise of amplifiers and about the beauty and power of modulation and synchronous detection. Circuit diagrams, calculations, and simulations are all very necessary, but whatever measurements you want to do, at some point you must put the theory into practice and build something! Sure, things will go wrong and not work as you hoped, so it is important to learn about the limitations and practical problems of electronics and optoelectronics in this environment, debugging the problems and figuring out what caused them. In my experience this means making lots of circuits, so you don t want to waste time searching for circuit fragments to do the job or actually constructing them. In general, the same needs and problems crop up time and again. Hence it is useful to have a collection, initially just designs but over time a physical collection, of the key circuits. Source drivers, synchronous detectors, clock oscillators and so on will be very useful in quickly assembling experiments; it is the flux of these experiments, properly evaluated, that generates experience. Later in this chapter we give a small collection of the electronic clich s you will need, together with some suggestions for actual components. Generally the circuits are rather trivial, but not if you need to search hours for them...