E7D07
PRACTICAL CIRCUITS · Power supplies and voltage regulators; solar array charge controllers
E7D07E7D →
What is the purpose of C2 in the circuit shown in Figure E7-2?
- AIt bypasses rectifier output ripple around D1
- BIt is a brute force filter for the output
- CTo prevent self-oscillation
- DTo provide fixed DC bias for Q1
Why In Figure E7-2 the zener D1 sets the reference voltage for the series pass transistor Q1, and C2 sits in parallel with that zener. A capacitor is a low impedance to AC and an open circuit to DC, so C2 shunts the leftover rectifier ripple and the zener's own noise to ground while leaving the DC reference level untouched. A cleaner reference means the regulator's output follows a steadier voltage, since the emitter of Q1 tracks the reference less one diode drop.
Watch out The brute force filter idea describes the large input capacitor right after the rectifier, which smooths the raw pulsating DC, not the small capacitor sitting across the zener reference.
Cap across the zener = ripple and noise shunt for the reference, not the main output filter.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
The rest of E7D
- E7D01 How does a linear electronic voltage regulator work?
- E7D02 How does a switchmode voltage regulator work?
- E7D03 What device is used as a stable voltage reference?
- E7D04 Which of the following describes a three-terminal voltage regulator?
- E7D05 Which of the following types of linear voltage regulator operates by loading the unregulated voltage source?
- E7D06 What is the purpose of Q1 in the circuit shown in Figure E7-2?
- E7D07 What is the purpose of C2 in the circuit shown in Figure E7-2?
- E7D08 What type of circuit is shown in Figure E7-2?
- E7D09 How is battery operating time calculated?
- E7D10 Why is a switching type power supply less expensive and lighter than an equivalent linear power supply?
- E7D11 What is the purpose of an inverter connected to a solar panel output?
- E7D12 What is the dropout voltage of a linear voltage regulator?
- E7D13 Which of the following calculates power dissipated by a series linear voltage regulator?
- E7D14 What is the purpose of connecting equal-value resistors across power supply filter capacitors connected in se…
- E7D15 What is the purpose of a step-start circuit in a high-voltage power supply?