A cascaded op amp set up is a head-to-tail arrangement of two or more op amps in a single circuit. The output voltage from the first op amp becomes the input voltage for the second, etc. In this lab, we designed a temperature measurement system which implements a wheatstone bridge, pictured below:
A thermistor was used as R + delta R, since it its a resistor that changes with change in temperature. A poteniometer was used to match the initial resistance of the thermistor, which balanced out the bridge, causing V_ab = 0. As the thermistor gained heat, there becomes a difference in resistance, and thus a potential difference between a and b. This voltage will be directed into an op amp, which was used to tone down the sensitivity of the wheatstone bridge.
We began by drawing a diagram of our proposed design and figuring out what the gain needed to be in order to have our temperature measuring system range between 0 and >2 V:
Wheatstone Bridge
Full Circuit with balanced wheatstone bridge
Output voltage achieved was 2.64 V, near the expected 2.3 V
In Class Examples
1. Practice: Find io as a function for vs.
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