A sensor converts a physical quantity (such as heat, pressure, vibration, etc.) to an electrical signal. It

Question:

A sensor converts a physical quantity (such as heat, pressure, vibration, etc.) to an electrical signal. It is modeled by a voltage source v_s in series with an internal resistance r. The sensor feeds a load R as in Fig. 5-61

(a). It is desired that the load current i be proportional to voltage v_s regardless of the load. Design a circuit (including the elements’ values) which provides such a function.

(b). If r = R₁R₃/R₂, the op amp circuit (internal resistance −r) in combination with the sensor (internal resistance r) presents an ideal current source (zero internal resistance). The range of operation will be limited by the op amp’s saturation levels. 3 im (a) R 2 R www R (b) ww ww R3 R