Homework 7 solutions 2

# Homework 7 solutions 2 - Homework 7 1. A temperature sensor...

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1 Homework 7 1. A temperature sensor is put into the following circuit as R s . An identical, matching reference sensor R ref is held at 37 °C. a) What is the output voltage E out ? Show your work. The upper and lower circuits on the left hand side are identical in form. The equations we need for this first stage are E + = E - = 0 I 1 = E in /R 1 I s = -E o1 /R S I s = I 1 Combining these gives -E o1 /R S = E in /R 1 E o1 = -E in R S /R 1 Likewise, E o2 = -E in R ref /R 1 The next stage is a follower. By inspection, E o3 = E o1 and E o4 = E o2 . (I 2 , I 3 , I 7 , and I 8 = 0) The equations we need for the third stage are E + = E - E + = E o4 R 3 /(R 2 + R 3 ) I 4 = (E o3 - E + )/R 2 I 5 = -(E out - E + )/R 3 I 5 = I 4 Combining these gives 40 pts

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2 () ( ) 3 3 2 33 03 4 3 2 3 3 4 3 2 3 22 43 2 3 2 3 3 3 3 2 3 3 23 2 2 2 2 1 out o out o o o ooo oo R EE E E R RR E E E E ER/R R E E R R R R R R R R R ++ −= =− = + + ⎡⎤ =+ + + ⎣⎦ ⎛⎞ + = ⎜⎟ ⎢⎥ ⎝⎠ =−= 3 2 R R Now replacing E o3 and E o4 , 3 21 1 1 1 2 ref S out o o in in in S ref R R R E E E E R R R R R R = += b) What is the purpose of each of the amplifiers?
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## This note was uploaded on 11/28/2010 for the course ENES enes100 taught by Professor Staff during the Spring '10 term at Maryland.

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Homework 7 solutions 2 - Homework 7 1. A temperature sensor...

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