🔍 Key Concepts

• Count the number of leads/terminals on each device and relate that to how many connections a bipolar junction transistor (BJT) requires (emitter, base, collector). • Recognize common package styles: small diode, bridge rectifier, power diode, and transistor/MOSFET packages. • Think about which devices normally have two leads, which have three leads, and which have four or many leads.

💭 Think About

• Which pictured devices are clearly NOT BJTs based on having only two leads or many leads? Eliminate those first. • Among the remaining pictures, which package style most commonly represents a three‑terminal transistor used for switching or amplification? • Look for the device whose metal tab or mounting hole is often used as a heat sink for a three‑lead transistor package.

✅ Before You Answer

• Verify that a BJT must have three electrical connections: emitter, base, and collector. • Confirm which illustration shows exactly three leads coming out of the plastic body (ignoring any mounting hole or tab). • Double‑check that the devices you ruled out are recognized forms of diodes, bridge rectifiers, or integrated circuits, not discrete BJTs.