ELEC 243 Lab

Introduction

Last week we looked at several op-amp for amplifying voltages. While there are many things you can do with a voltage amplifier, there are also many things that you can't. In particular, the optoelectronic transducers we studied in Experiment 2.3 have nonlinear behavior in terms of their voltages, but very linear behavior in terms of current. To effectively utilize these, we will need amplifiers which accept and deliver currents rather than voltages.

Some of our other transducers are resistive: they produce neither voltages nor currents on their own, but must be used in conjunction with voltage or current sources to produce a usable signal. For transducers which produce large changes in resistance in response to the physical quantity being measured, the circuits we used in Labs 3 and 4 are satisfactory. However some transducers, such as strain gages, produce only very small changes in resistance. For satisfactory results with these, we will need a new circuit: the bridge.