Hello All,
I'm working on a project that calls for a linear response 1-3% accurate ohmmeter in an embedded form factor (very small, very low power consumption). In my research I settled on the circuit pictured below but I don't feel I completely understand how it works. It seems like the LM334 and LM336 are set up in a configuration which will provide an minimum temp coefficient voltage reference which is then supplied to an (manually) adjustable voltage divider. The output at the central node of this divider is then supplied to a voltage follower op-amp circuit. I believe that the purpose of connecting the negative feedback loop of the voltage follower to the zener diode (LM336) anode is to "feed-forward" the voltage reference such that the reponse to increasing R_sense is linear rather than negatively exponential. Is my interpreation correct? Any help understanding how this circuit works or how to break it down into seperate functional elements would be greatly appreciated. Thanks!
I'm working on a project that calls for a linear response 1-3% accurate ohmmeter in an embedded form factor (very small, very low power consumption). In my research I settled on the circuit pictured below but I don't feel I completely understand how it works. It seems like the LM334 and LM336 are set up in a configuration which will provide an minimum temp coefficient voltage reference which is then supplied to an (manually) adjustable voltage divider. The output at the central node of this divider is then supplied to a voltage follower op-amp circuit. I believe that the purpose of connecting the negative feedback loop of the voltage follower to the zener diode (LM336) anode is to "feed-forward" the voltage reference such that the reponse to increasing R_sense is linear rather than negatively exponential. Is my interpreation correct? Any help understanding how this circuit works or how to break it down into seperate functional elements would be greatly appreciated. Thanks!