Advanced Qualification · A-002 Advanced components and circuits · A-002-005-011
Which of the following is a PNPN device?
- A Zener diode
- B Silicon controlled rectifier (SCR)
- C PIN diode
- D Hot carrier (Schottky) diode
Correct answer: B — Silicon controlled rectifier (SCR). From the official ISED question bank, verified word for word.
Why
A Silicon controlled rectifier (SCR) is the correct choice because it is built from four alternating layers of silicon, creating a P-N-P-N structure that acts like a switch you can turn on with a small signal but cannot turn off easily. The full explanation — and one for every question — is in Pro.
Practise this section
Advanced components and circuits: semiconductors, amplifier classes, oscillators, mixers, filters and digital logic.