Power Supply

• Every electronic circuit needs a power source. The most common type takes the 120-volt alternating current (AC) from your household outlet and converts it to direct current (DC) of between 3 and 24 volts. The simpler approach uses a step-down transformer, rectifier and capacitors to produce a lower-voltage DC. A regulator chip holds the voltage steady despite changes in a circuit's power demands. A more complex design converts AC to a high-frequency signal, which then passes through a smaller, more energy-efficient transformer to reduce its voltage.
  
  

Op Amps

• Operational amplifiers, or op amps, are integrated circuits (ICs) you can treat as electronic building blocks. These are linear devices, meaning they work with standard audio and DC signals. You can start with very simple circuits consisting of the op amp and a few resistors, then work your way up to oscillators, filters and other signal-processing applications.
  
  

PIC Controller

• As your circuit-building skills progress, you can tackle a PIC (programmable interface controller) microprocessor project. A PIC circuit combines the hardware you build with software you program into the PIC. The circuits can be very simple to build, having only a handful of parts. The real power comes in the programs you write. Since the PIC chip can both send and receive signals, you can write signal generator programs, timers and sophisticated controllers. As the electronic world becomes increasingly digital, any PIC projects you build will serve you well.
  
  

FM Radio

• Any well-rounded electronics education should include some exposure to radio circuits. The high frequencies involved in radio circuits involve some black magic in design -- you learn that signals in a poorly-built circuit will jump around in unexpected ways. You can start with simple transmitters and receivers and work your way up to stereo, frequency-synthesized tuning and other features.