Fixed regulators by number For a standard 78xx series linear regulator, what regulated DC output does a 7814 provide under proper operating conditions?

Difficulty: Easy

Correct Answer: +14 V dc

Explanation:


Introduction / Context:
The 78xx family are positive fixed-output linear regulators used in countless power supplies. The “xx” suffix indicates the nominal output voltage. Knowing these at a glance speeds up design and troubleshooting when scanning a board or a parts bin.


Given Data / Assumptions:

  • Device is a 7814 from the 78xx family.
  • Proper input voltage headroom and heat sinking are assumed.
  • Standard pinout and positive regulation behavior apply.


Concept / Approach:

For 78xx regulators, “xx” corresponds to the output voltage in volts. Examples: 7805 → +5 V, 7812 → +12 V, 7815 → +15 V. Therefore, 7814 provides a regulated +14 V DC output. The companion negative series are 79xx (e.g., 7912 for –12 V), not to be confused with 78xx.


Step-by-Step Solution:

Identify series: 78xx → positive regulator.Read suffix: “14” → 14 volts nominal.Conclude output: +14 V DC (with tolerance per datasheet).


Verification / Alternative check:

Datasheets from multiple vendors list VO = +14 V typical for 7814, with dropout and line/load regulation specs ensuring stable +14 V when input exceeds VO + dropout.


Why Other Options Are Wrong:

  • –14 V dc: negative outputs belong to 79xx series.
  • ±8 V options: wrong suffix and wrong polarity for 78xx family.


Common Pitfalls:

  • Confusing 7815 (15 V) with 7814 (14 V).
  • Ignoring dropout; if input is too low, regulation will be lost.


Final Answer:

+14 V dc

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