Medium

LC Tank Circuit Demonstrator

A coil and a capacitor in parallel form a "tank circuit" that resonates at a specific frequency — the basic principle behind every radio or transmitter.

Circuit Diagram

+9V L inductor C ceramic 100pF Q BC547 B ← feedback C E → small R → GND C (collector) bias R C feedback LC tank sets the frequency — hold an AM radio nearby to hear it

How to Build It

  1. Connect the inductor and ceramic capacitor in parallel — this is the LC tank circuit.
  2. Connect this assembly between a BC547 transistor's collector and the positive rail.
  3. Connect a bias resistor from the positive rail to the transistor's base.
  4. Connect a small feedback capacitor from the collector back to the base, to sustain oscillation.
  5. Connect the emitter to GND through a small resistor.
  6. Power the circuit — use a nearby AM radio to detect the oscillation (you'll hear a static tone when the radio is tuned to the circuit's frequency).

Bill of Materials

ProductCodeQty
Inductor MCQ1V1608-R470-R 1
Capacitor (electrolytic/ceramic/SMD/film) #N/A 1
Capacitor (electrolytic/ceramic/SMD/film) CC-100 1
Resistor DR47K-8/9 1
Transistor (incl. IGBT) 1
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