Question

A Rī thermistor whose temperature coefficient is a = -0.02 per degree ( with a=(1/RI)dR,/dt et R1 = 5.2 K2 at 20°C ) is placed in the circuit of the following figure, circuit comprising an ideal OP-AMP supplied with + 10 V. Vo L R2 I vol TTT TT TIL 1) What is the output s of the circuit at 20 ° C worth? 2) Determine the RT expression used to toggle the output of the circuit. 3) What is the use of such a device?

Answer 1

Given Creuil is a Comparator circuit used to detect the difference at its input and generates a corresponding autput - RI (a) for the circuit s is given by SH S=AV - V.) (vt = Voltage al positive nace of ophaup V-a voltage of negative node of op anp V4= = Vo Rz Ri+R2 Voir RIART S = A[VORI - VO R2 R, TRT Rit Rz] S = A vol RI - R2 ] RIHRT Rit R2 20°C RTZ 5.261 Sz Avo I RI - Rz LR1+5.2 KN R,+R2J at [Az gains of op aup]

(%) A = very large ท Ou97 C22277,024 S = AVOIRI - R27 R, TRT RitRq. If R > R2. S=tlov R,HRT R,+R2 Ric R2 S =-lov Ritra Ritra so toggle et Ri e zo Re - RitRT X RitR2 R, CR, +R2) = R2 CR, + R) A R? +R, Rz z. R2 R + R, R2 R, -= Ri= RTR₂ R² Rz - The device as using a Thermistor can be used to detect the change in temperature . As the temperature changes the output toggles between tlor and - lov