Optoelectronic Device Identification
Optoelectronic devices exchange electrical and optical energy through carrier generation or recombination. Identification should use operating mode and characteristic curves, not device name alone.
Why this shows up in the exam
Matching devices to characteristic curves · Distinguishing emitters, detectors, and generators · Interpreting wavelength and band-gap questions
Learn the idea
Bias direction, response quantity, and band-gap relation distinguish LED, photodiode, solar cell, and related devices. An LED emits under forward bias, a photodiode senses light usually in reverse bias, and a solar cell generates power without external bias. Their graphs reveal which quantity responds to voltage or light.
🧠 Memory hook: LED emits, photodiode detects, solar cell delivers.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- E_photon = h nu = h c / lambda — common energy relation connecting optical wavelength and electronic transitions
How to approach it
- 1Ask whether light enters or leaves the device
- 2Check external-bias direction
- 3Use curve axes and units before choosing a device
Common slip-ups that cost marks
- •Identifying a device from one unlabeled curve feature
- •Using the same bias rule for all optical devices
- •Treating OCR-fragmented diagrams as fully verified evidence
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A transistor has common-emitter current gain beta = 50. If base current is 20 microA, find collector current.
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