Analog Circuits

Introduction to Analog Circuits

Analog circuits process continuous signals that can have any value within a range. Unlike digital circuits that work with discrete 0s and 1s, analog circuits handle real-world signals like sound, temperature, and light intensity.

These circuits are fundamental to audio equipment, radio communication, sensors, and power management systems.

Operational Amplifiers (Op-Amps)

The operational amplifier is the building block of analog electronics. It's a high-gain differential amplifier with two inputs and one output.

Ideal Op-Amp Characteristics

  • Infinite input impedance (no current drawn from inputs)
  • Zero output impedance (can drive any load)
  • Infinite open-loop gain
  • Infinite bandwidth
  • Zero offset voltage

Inverting Amplifier

Where Rf is the feedback resistor and Rin is the input resistor.

Example: If Rf = 100kΩ and Rin = 10kΩ, then Av = -10

Non-Inverting Amplifier

The non-inverting amplifier maintains signal polarity and has very high input impedance.

Analog Filters

Filters are circuits that allow certain frequencies to pass while blocking others.

Low-Pass Filter

Allows frequencies below the cutoff frequency fc to pass.

High-Pass Filter

Allows frequencies above the cutoff frequency to pass.

Band-Pass Filter

Allows a specific range of frequencies to pass through.

Practical Applications

  • Audio Systems: Amplification, tone control, equalization
  • Sensors: Signal conditioning for temperature, pressure, light sensors
  • Power Supplies: Voltage regulation and control
  • Communication: Modulation, demodulation, filtering
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