GATE EE 2021 Set 1 — Question 62
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Analog & Digital Electronics → Operational Amplifiers → Comparator & Schmitt Trigger
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Question
A CMOS Schmitt-trigger inverter has a low output level of and a high output level of . It has input thresholds of and . The input capacitance and output resistance of the Schmitt-trigger are negligible. The frequency of the oscillator shown is ______ . (Round off to 2 decimal places.)
Correct answer
3150 to 3170
Solution
From the figure, is the feedback resistor from the inverter output to its input, and is from the input to ground, so .The capacitor voltage is the Schmitt-trigger input. It oscillates between the thresholds and , charging towards whatever the (inverting) output is.
1.Charging phase (output high, ): the input has just fallen to , so the output is high and charges from towards until it reaches .
2.Discharging phase (output low, ): the input has reached , the output goes low and discharges from towards until it reaches .
3.Period and frequency:
Rounded to two decimal places, .Continue learning with Success Tracker
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