Operational Amplifier Fundamentals Unit 8 – Voltage Comparators
Exercise 2 – Zener-Clamped Operation
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to operate a zener-clamped op amp
comparator circuit using dc and ac voltages. You will verify your results with an oscilloscope.
EXERCISE DISCUSSION
- In the circuit for this exercise, a zener diode (CR1) completes the feedback path for U1.
- U1 is zero based because its noninverting terminal is connected to circuit common.
Therefore, the circuit reference voltage is 0V. - If VI is positive (greater than 0V), VO swings in a negative direction toward -VSAT.
- When VO approximately equals the zener breakdown voltage (VZ), CR1 conducts and
provides negative feedback. The feedback clamps VO to the value of VZ and prevents
negative saturation. - Based on the placement of CR1 (anode lead to U1 output terminal) in the circuit, VO switches
between -VZ and +VF. - A zener-diode-clamped circuit controls the levels of a sine wave or square wave input signal.