7.1 The 555 Timer IC

An 8-pin IC used for generating accurate time delays and oscillations (non-sinusoidal waveforms). Its internal structure includes:

• A voltage divider network with three 5kΩ resistors.
• Two comparators.
• An SR flip-flop.
• Transistors and an inverter. It can operate in monostable mode (to produce a single pulse) or astable mode (to produce a continuous square wave).

7.2 The Phase Locked Loop (PLL) IC 565

A vital block in communication systems, the PLL consists of a phase detector, an active low-pass filter, and a Voltage Controlled Oscillator (VCO). The PLL operates to match the VCO’s output frequency to an input signal’s frequency. It functions in three modes: free running, capture, and lock. The IC 565 is a common 14-pin PLL IC.

7.3 Voltage Regulator ICs

These ICs maintain a constant DC output voltage despite fluctuations in input voltage or load current.

• Fixed Voltage Regulators:
  • 78xx series: Produce fixed positive DC voltages (e.g., 7805 produces +5V).
  • 79xx series: Produce fixed negative DC voltages (e.g., 7905 produces -5V).
• Adjustable Voltage Regulators:
  • LM317: A 3-pin IC that produces a positive DC output adjustable over a range (e.g., 1.25V to 37V).