Calculating Gain and Vout for Op-Amp Sensor Circuit with Variable Resistance Sensor

The discussion addresses calculating the gain and output voltage (Vout) of an op-amp sensor circuit using a variable resistance temperature sensor (thermistor). The sensor resistance varies with temperature: 5kΩ at 0°C, 2.5kΩ at 20°C, 2kΩ at 30°C, and 1.8kΩ at 40°C. The circuit is divided into two stages with operational amplifiers: the first op-amp configured as a non-inverting amplifier with a gain of 2, and the second as a unity gain buffer. The output voltage is derived from the voltage divider formed by the thermistor (Rtheom) and a fixed 5kΩ resistor, multiplied by the gain of the first op-amp stage. The formula for output voltage is approximately Vout = Vin * (Rtheom / (Rtheom + 5kΩ)) * Gain, where Vin is the supply voltage (commonly 5V or 10V). The output voltage range depends on the thermistor resistance at different temperatures and the op-amp supply voltage, which should exceed the maximum expected output voltage. Clarifications were made on the term "Rtheom" referring to the thermistor resistance and the gain calculation based on non-inverting amplifier principles. The discussion emphasizes verifying node voltages and supply levels to avoid output saturation.
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