🔍 Key Concepts

• Operational amplifier (op-amp) inputs: meaning of the inverting (-) and non-inverting (+) inputs • How a comparator or differential amplifier decides output polarity based on which input is more positive • Use of a Wheatstone bridge sensor feeding the amplifier and how its unbalance changes which node is more positive

💭 Think About

• Look at figure B: which terminal is labeled with the plus sign and which with the minus sign, and what signals are applied to each? • From basic op-amp behavior, what happens to the output when the non‑inverting (+) input voltage becomes higher than the inverting (-) input voltage? What about the opposite case? • Compare that basic behavior with the graph in figure C: when the input (sensor) voltage is greater than the reference voltage, is the output shown as positive or negative?

✅ Before You Answer

• Confirm which lead in figure A and B is the inverting (-) input and which is the non‑inverting (+) input of the differential amplifier. • Verify from the sketch in C whether sensor > reference corresponds to a positive or negative output region on the graph. • Make sure the wording in the choice you select exactly matches the rule: “more positive input on (+) gives ____ output; more positive input on (-) gives ____ output.”