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GATE 2015 EE (EE2) – Question 63

Control Systems · Transient and Steady-state analysis of linear time invariant systems · 2 marks · Multiple choice

Which graph is the unit-step response of $G(s)=(1-2s)/(1+s)$?

Diagram for GATE 2015 EE (EE2) question 63
  1. Option A in the figure
  2. Option B in the figure
  3. Option C in the figure
  4. Option D in the figure

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Show answer and explanation

Correct answer: (A) Option A in the figure

Explanation

For a unit step, Y(s)=(1−2s)/[s(s+1)]. Partial fractions give Y=1/s−3/(s+1).

Thus y(t)=1−3e⁻ᵗ for t≥0. It jumps initially to −2, then rises monotonically to 1. Only graph **A** has those initial and final values and that shape. The instantaneous jump comes from the transfer function's nonzero direct-feedthrough term.

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