🔍 Key Concepts

• Identify what section B (diodes) is doing to the AC from the transformer and how that affects what arrives at section C and then D • Recall the difference between a filter (L and C smoothing ripple) and a voltage regulator (keeping output nearly constant despite load/line changes) • Look at components in section D: a transistor, a resistor, and a diode symbol with a bent line (hint: often a Zener reference) and think about what type of circuit usually uses that combination

💭 Think About

• First, decide which section of the circuit is already performing the rectification; then ask yourself what job is left for section D to do • Consider how the output at TP4 (after L1 and C1) compares to the desired steady DC at TP5; what extra function is needed beyond filtering to keep the voltage stable as load changes? • Ask which choice best matches a circuit that uses a transistor controlled by a reference diode to control the voltage delivered to the load

✅ Before You Answer

• Verify which section (A, B, C, or D) changes AC to DC; that section will match choice C) a rectifier, so section D must be doing something else • Confirm that L1 and C1 together form the classic filter network, so compare that with choice A) a filter • Note that the presence of a control transistor and a reference diode feeding the load is characteristic of a voltage control function; check which option corresponds to that