Question

Given that the charging current of capacitor is constant in a monostable multivibrator using IC 555, then find the type of output waveform, type of capacitor voltage waveform and the time period of output.

(a) The capacitor waveform is a ramp, the output waveform is sinusoidal, the time period is \(\frac{2.C.VCC}{3.I}\)

(b) The capacitor waveform is a ramp, the output waveform is a pulse, the time period is \(\frac{2.C.VCC}{3.I}\)

(c) The capacitor waveform is a ramp, the output waveform is a pulse, the time period is \(\frac{C.VCC}{3.I}\)

(d) The capacitor waveform is a ramp, the output waveform is a ramp, the time period is \(\frac{2.C.VCC}{3.I}\)

I have been asked this question during an interview.

Enquiry is from Different Types of Multivibrators topic in section Multivibrators of Analog Circuits

Answer 1

The correct choice is (b) The capacitor waveform is a ramp, the output waveform is a pulse, the time period is \(\frac{2.C.VCC}{3.I}\)

Easy explanation: If a constant charging current is applied through the capacitor, the output is a pulse, while capacitor voltage is a ramp.

Time period of ramp/pulse = TO = 2VCCxC/3I.