Question

9. Open ended design question. There is no one right answer. Design an amplifier circuit to interface the thermistor half bridge shown below to the ADC in the TM4C123. Use single supply op amp techniques for your design. Show the calculations that lead to your design (Hint the concepts needed for this design were covered in lectures 15 and 16) (55 pts) 3.3 V TM4C123 S10k Your Circuit Van >10 kQ+AR Thermistor Circuit Requirements The input voltage to your circuit ranges from 1.617 volts to 1.683 volts. The input to your circuit is the output from the half bridge thermistor circuit. The thermistor will be sampled at 10 Hz Things to consider for your design, gain, filtering, biasing etc. Be sure to draw your complete circuit schematic. The schematic should show all required voltages and ground connections required for your design. Include values for the components used in your design such as resistors and capacitors.

Answer 1

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          Please find the answer attached as under. Please give a thumbs up rating if you find the answer useful! Have a rocking day ahead!

The input range to your circuit is 1.617 to 1.683, which is 1.683 - 1.617 = 0.0660V. Assume that the same Vref = 3.3V is used for the ADC as well. Thus, the ADC input will accept analog inputs from 0 till 3.3V. Thus, the slope of the transfer function = 3.3/0.0660 = 50. Also the output of the circuit is 0V when the input is 1.617V. Thus, the y-offset is -50*1.617 = -80.85. Thus, the function needs to be: y = 50x - 80.85 = 50(x-1.61)

This is achieved by the circuit below:

1.61 Yvon

To achieve a gain of 50, R2/R1 = 50. Put R2 =50K and R1 = 1k. Also R3 = 50K and R4 = 1K

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