Find the Impulse Response of a Circuit

Find the impulse response for a circuit that is composed of a resistor and an inductor , and is driven by a time-dependent voltage .

The current can be computed by solving a linear first-order differential equation .

Set up the differential operator corresponding to the left-hand side of the ODE.

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voltage = L i'[t] + R i[t];

Assume that the switch is initially open.

In[2]:=

init = i[0] == 0;

Compute the impulse response for the circuit using GreenFunction.

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gf[s_, t_] = GreenFunction[{voltage, init}, i[t], {t, 0, \[Infinity]}, s]

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Plot the impulse response at .

In[4]:=

Plot[gf[s, t] /. {s -> 1, R -> 2, L -> 4}, {t, 0, 7}, PlotTheme -> "Scientific", AxesLabel -> {"t", "i[t]"}]

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Compute the response of the circuit to a step voltage.

In[5]:=

v[t_] := HeavisideTheta[t];

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current = Integrate[gf[s, t] v[s], {s, 0, t}, Assumptions -> t > 0]

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Visualize the step response.

In[7]:=

Plot[{current /. {R -> 2, L -> 4}, 0.5} // Evaluate, {t, 0, 6}, PlotTheme -> "Scientific"]

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