FE Electrical & Computer Practice Question Solution included after investigation
CASE E-028 · FE

The Op-Amp That Tried to Output -10 V on ±5 V Rails

The gain equation requests -10 V, but the amplifier only has ±5 V rails.

▶ INTERACTIVE CASE FILE • 5–10 MIN • CLICK TO INVESTIGATE

Inspect, commit, prove, fix, and sign off.

Case E-028 engineering failure visual
HOW THIS WORKS

Think like
a real engineer.

Follow the investigation process used in the field — in five guided steps.

1

Inspect

Review the problem, diagram, and evidence.

2

Commit

Choose your hypothesis.

3

Prove

Run calculations and test your idea.

4

Fix

Select and validate a safe correction.

5

Sign Off

See the full debrief and key takeaways.

Case Brief

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

An inverting op amp has R1 = 10 kΩ, Rf = 20 kΩ, Vin = +5 V, and ±5 V supplies. The ideal gain formula requests -10 V, but the real output cannot go beyond the negative supply limit and saturates.

Electronics Electrical & Computer Design Verification Root Cause Analysis Safe Correction
E-028
INVESTIGATION WORKSPACE WORK THROUGH THE CASE — YOUR CHOICES MATTER.
🔒
DEBRIEF (LOCKED)

Complete the investigation
to unlock the full debrief.

Find the root cause, confirm the fix, and see how this connects to the exam.

🔒Root causeComplete the case
to reveal
🔒Correct fixComplete the case
to reveal
🔒Exam takeawayComplete the case
to reveal
CASE CLOSED · ENGINEERING VERDICT

What actually failed — and what should change.

What was missed

Using the ideal gain formula without checking the requested output against supply/output limits.

Corrected model

An inverting gain of -2 with a +5 V input requests -10 V. With ±5 V supplies, the op amp cannot remain linear and saturates near the negative rail.

QUICK ANSWER

An inverting gain of -2 with a +5 V input requests -10 V. With ±5 V supplies, the op amp cannot remain linear and saturates near the negative rail.

ENGINEERING TAKEAWAY

Check the device model and operating region first, then apply the corresponding circuit equation.

CASE QUESTIONS

Questions this case should settle.

Why does the op amp saturate in this case?

The ideal gain equation requests -10 V, but the negative supply rail is only -5 V.

What is the ideal inverting gain?

-Rf/R1 = -20 kΩ/10 kΩ = -2.

NEXT FE PRACTICE QUESTION

The Transistor That Refused to Amplify 100×

Electronics · 5–10 min

Continue Practice →
WHAT YOU’LL LEARN

Real failures. Lasting skills.

Each case is designed to build the judgment, analysis, and confidence you need for engineering exams — and beyond.

  • Apply core engineering concepts to real-world problems
  • Practice structured troubleshooting and analysis
  • Strengthen exam-ready thinking through realistic scenarios
COMMON QUESTIONS
Do I need prior knowledge to use these cases?

Basic subject familiarity helps, but every case is designed to teach through the investigation itself.

How long does a case take?

Most cases are designed for a focused 5–10 minute investigation.

Are the cases aligned with engineering exams?

Each case is mapped to a verified exam, subject, topic, and misconception before publication.

What happens after I complete a case?

The sealed debrief unlocks with the root cause, corrected reasoning, fix, and takeaway.