7.4.3.1 Inverting Comparator With Hysteresis

The inverting comparator with hysteresis requires a three resistor network that is referenced to the supply voltage V⁺ of the comparator as shown in Figure 19. When V_IN at the inverting input is less than V_A, the voltage at the noninverting node of the comparator (V_IN< V_A), the output voltage is high (for simplicity assume V_O switches as high as V⁺). The three network resistors can be represented as R₁//R₃ in series with R₂.

Figure 19. Inverting Comparator With Hysteresis

The lower input trip voltage V_A1 is defined as:

When V_IN is greater than V_A, the output voltage is low or very close to ground. In this case the three network resistors can be presented as R₂ // R₃ in series with R₁.

The upper trip voltage V_A2 is defined as:

The total hysteresis provided by the network is defined as ΔV_A = V_A1 - V_A2.

Equation 3.