Where: V₀ = V₁ + V₂ − V₃ – V₄
(V₁ + V₂ ≥ (V₃ + V₄) to keep V₀ > 0V_DC

Figure 6-8 DC Summing Amplifier (V_IN ≥ 0V_DC and V_O ≥ V_DC

For

(CMRR depends on this resistor ratio match)

As shown: V_O = 2(V₂ − V₁)

Figure 6-9 High Input Z, DC Differential Amplifier

Figure 6-10 Photo Voltaic-Cell Amplifier

If R1 = R5, R3 = R6, and R4 = R7; then

∴A_V ≈ 100 for circuit shown (R₂ = 9.3k).

Figure 6-11 Instrumentation Amplifier

Figure 6-12 Rail-to-Rail Single Supply Low Pass Filter

This low-pass filter circuit can be used as an antialiasing filter with the same supply as the ADC. Filter designs can also take advantage of the LMC649x ultra-low input current. The ultra-low input current yields negligible offset error even when large value resistors are used. This configuration in turn allows the use of smaller-valued capacitors that take up less board space and cost less.

Figure 6-13 Low Voltage Peak Detector with Rail-to-Rail Peak Capture Range

Dielectric absorption and leakage is minimized by using a polystyrene or polypropylene hold capacitor. The droop rate is primarily determined by the value of C_HOLD and diode leakage current. Select low-leakage current diodes to minimize drooping.

R_f = Rx
R_f >> R1, R2, R3, and R4

Figure 6-14 Pressure Sensor

In a manifold absolute pressure sensor application, a strain gauge is mounted on the intake manifold in the engine unit. Manifold pressure causes the sensing resistors, R1, R2, R3 and R4 to change. The resistors change in a way such that R2 and R4 increase by the same amount R1 and R3 decrease. This causes a differential voltage between the input of the amplifier. The gain of the amplifier is adjusted by R_f.