Operational Amplifiers (Op-Amps)

1. Definition

1.1 What is an Op-Amp?

An Operational Amplifier, or Op-Amp, is a special kind of electronic chip that can make weak signals much stronger.
It has two inputs and one output, and it compares the voltages at the inputs.

Think of it like a “volume knob” for voltage, it can amplify tiny voltages from a microphone, sensor, or antenna so other circuits can use them.

Op-Amp examples

Op-Amp Symbol

Op-Amp symbol

1.2 Common Op-Amp ICs

  • LM741 : classic, general-purpose op-amp.
  • TL081 : low-noise op-amp, good for audio.
  • LM358 : dual op-amp, works well with low voltage.

2. Features

  • High input impedance : doesn’t load down the signal source.
  • Low output impedance : can drive the next stage easily.
  • Very high voltage gain : can amplify signals thousands of times.
  • Can be set up for many jobs: amplification, filtering, comparing voltages, etc.

4. How to Use

Safety Note

Never apply a voltage higher than the op-amp’s power supply.
Doing so can damage the chip.

4.1 Pin functions (LM741 example)

  1. Offset Null (-) : Fine adjustment for perfect zero output.
  2. Inverting Input (-) : Signal here is amplified but inverted (flipped).
  3. Non-inverting Input (+) : Signal here is amplified without inversion.
  4. V- : Negative supply voltage (or ground in single-supply circuits).
  5. Offset Null (+) : Fine adjustment.
  6. Output : Amplified signal comes out here.
  7. V+ : Positive supply voltage.
  8. NC : No internal connection.

4.2 Basic Inverting Amplifier Example

If you connect an op-amp with two resistors like this:

  • Rin between your signal and the inverting input (-)
  • Rf between output and inverting input (-)
  • Non-inverting input (+) connected to ground

The gain (how much it amplifies) is:

Gain = - Rf/Rin

Example:

  • Rin = 10 kΩ
  • Rf = 100 kΩ
  • Gain = -10 (signal is 10× bigger and inverted)

4.3 Common Applications

  • Audio amplifiers : boost microphone or guitar signals.
  • Filters : remove noise or unwanted frequencies.
  • Comparators : detect when one voltage is higher than another.
  • Signal conditioning : prepare sensor signals for a microcontroller.

5. Video Explanation

video coming soon