High Bias Design Problem
A particular pressure sensor is designed to operate under constant pressure. The task is to detect a pressure increase and sound an alarm. The sensor produces 1 mV at 100 psi, its usual operating pressure, and increases by 1 μV=psi.
The design must sound an alarm if the pressure reaches 150 psi. The transducer is modeled as a voltage source with a series resistor that varies with pressure from 50 Ω at 100 psi to 150 Ω at 150 psi.
Two types of OP AMPs are available. Type 1 are single-sided, meaning they have a + VCC of 5 V and a -VCC of 0 V. Type 2 OP AMPs are double-sided with a VCC of ±15 V and have a maximum closed-loop gain of 5000.
The alarm can be driven with the +5-V available from a saturated type 1 OP AMP. Only ± 15-V and +5-V sources are available. Design the alarm circuit.