The nominal output high of the comparator...

🔍 Key Concepts

• Comparator with hysteresis (Schmitt trigger) behavior and what “trip points” mean • How the reference voltage and feedback network (resistors) set the upper and lower switching thresholds • Relationship between output saturation level (4.5 V) and the actual input voltages that cause the comparator to switch

💭 Think About

• Ask yourself: Do the input trip points usually occur right at the output voltage level, or at some fraction of it set by a resistor divider? • Consider what happens when the output is at its high level (4.5 V): what voltage appears at the non‑inverting input through the feedback network, and at what input value will the comparator change state? • Repeat the same reasoning for when the output is low: what does that do to the threshold at the input?

✅ Before You Answer

• Verify that trip points are input voltages, not output voltages • Check whether the circuit in Fig. 8C11 includes positive feedback (hysteresis) using resistors from output to input • Confirm that the stated 4.5 V is the output high level, and compare that to the more realistic range for input thresholds (likely around a small fraction of the supply voltage, not at the rail).

The nominal output high of the comparator shown in Fig. 8C11 is 4.5 volts. Choose the most correct statement which describes the trip points.

Upper trip point is 4.5 volts. Lower trip point is approximately 0 volts.

Upper trip point is 2.5 volts. Lower trip point is approximately 2.0 volts.

Upper trip point is 900 microvolts. Lower trip point is approximately 0 volts.

Upper trip point is + 1 . 285 volts. Lower trip point is - 1 . 285 volts.

🔍 Key Concepts

💭 Think About

✅ Before You Answer