GATE 2016 EC (EC3) – Question 25
For the 555 astable multivibrator shown, the oscillation frequency at output pin 3 in kHz is ________.
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Correct answer: 5.55 to 5.75
Explanation
The capacitor charges through $R_A+R_B$ and discharges through $R_B$ between one-third and two-thirds of the supply. The period is $T=\ln2\,(R_A+2R_B)C$.
Substitute $R_A=2.2$ kΩ, $R_B=4.7$ kΩ and C=0.022 μF. This gives $T=0.00017689$ s.
Therefore **f≈5.653 kHz**, within the official 5.55–5.75 kHz range.