A lamp's intensity stays constant when monitored by an opto transistor-controlled feedback loop. When the voltage drops, the lamp's output also drops, and opto transistor Q1 draws less current. As a result, a power transistor conducts more heavily and charges a capacitor more rapidly [24]. The capacitor voltage controls the lamp voltage directly. A block diagram of the system is shown in Figure E2.7. Find the closed-loop transfer function, I(s)/R(s) where I(s) is the lamp intensity, and R(s) is the command or desired level of light.

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ls) Filter TS Opaque iube FIGURE E2.7 Lamp controller.