Operational Amplifier Fundamentals Unit 8 – Voltage Comparators
Exercise 1 – Open-Loop Operation
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to operate an open-loop comparator.
You will verify your results with a multimeter and an oscilloscope.
EXERCISE DISCUSSION
- U1 has very high gain: 50,000 or more.
- When configured for open-loop operation, U1 tends to saturate.
- When input voltage equals reference voltage the output voltage is at positive saturation.
- When input voltage is negative with respect to reference voltage the output voltage is at
positive saturation. - When input voltage is positive with respect to reference voltage the output voltage is at
negative saturation. - U1 switches between +VSAT and -VSAT as VI is adjusted slightly below or above VREF. This
point of operation is called the circuit trip point. - Since the range around the circuit trip point is small, the circuit threshold voltage is narrow.