Question

Identify diode, transistor, LED and I.C. from the given mixed collection.

Hint:

When identifying components, start with a visual inspection. The number of leads is a major clue: 2 for diodes/LEDs, 3 for transistors, and many more for ICs. The markings and shapes are also unique identifiers.

Answer 1

Step 1: Understanding the Components:
- Diode: A two-terminal electronic component that conducts current primarily in one direction. It has an anode (+) and a cathode (-).
- Transistor: A three-terminal semiconductor device used to amplify or switch electronic signals. Common types are Bipolar Junction Transistors (BJT) which have a Base, Collector, and Emitter.
- LED (Light Emitting Diode): A special type of diode that emits light when current flows through it. It also has two terminals, an anode and a cathode.
- I.C. (Integrated Circuit): A set of electronic circuits on one small flat piece (or "chip") of semiconductor material. It typically has multiple pins (legs) and is housed in a black rectangular package.
Step 2: Identification by Physical Appearance:
- Diode: Look for a small cylindrical component with two leads. It usually has a black body with a silver or white band on one end, which indicates the cathode (negative) side.
- Transistor: Look for a component with three leads (legs). It often has a flat face and a semi-circular body, typically black in color. Part numbers are printed on the flat face.
- LED: Look for a small, transparent or colored plastic bulb with two leads. One lead is typically longer than the other; the longer lead is the anode (+). The base of the bulb might have a flat side, which indicates the cathode (-).
- I.C.: Look for a black, rectangular "chip" with multiple pins arranged in two parallel rows. There is usually a notch or a dot at one end to indicate pin 1.
Step 3: Identification using a Multimeter (in Diode Test Mode):
- Diode/LED: Connect the multimeter probes to the two leads. In one direction (red probe to anode, black to cathode), the multimeter will show a small voltage reading (forward bias). In the reverse direction, it will show an open circuit ('OL'). An LED will also light up faintly when forward-biased.
- Transistor: Use the multimeter to find the 'base' terminal. The base will show a diode-like connection to the other two terminals (collector and emitter). For an NPN transistor, the base is P-type; connecting the red probe to the base and the black probe to the other two terminals will show a reading. For a PNP transistor, the base is N-type, so the black probe must be connected to the base.
- I.C.: An I.C. cannot be easily tested with a multimeter without knowing its internal circuit diagram (datasheet). Identification is primarily by its physical appearance and the part number printed on it.