ElectroHub
ComponentsActive / Semiconductor

Op-Amp

IC (Analog)

A high-gain differential amplifier building block. With feedback it does amplification, filtering, comparison and math on analog signals. Hugely versatile.

Schematic symbol

Operational amplifier

How op-amp appears in a circuit diagram.

Types & variants

General purpose (LM358, TL072)Rail-to-rail / single-supplyPrecision (low offset)High-speedComparators (related, e.g. LM393)

Key specs

Supply voltage

V

Single or dual rails; check it covers your signal range.

Gain-bandwidth product (GBW)

MHz

Trade-off between gain and bandwidth.

Slew rate

V/µs

How fast the output can change.

Input offset voltage

mV

Tiny built-in error; lower = more precise.

Rail-to-rail?

-

Whether in/out can swing to the supply rails.

Laws that govern it

  • Kirchhoff's current law (KCL)ΣI(in) = ΣI(out)

    Every gain formula you know is KCL at the inverting node: with the input drawing no current, the currents through Rin and Rf must cancel.

  • Kirchhoff's voltage law (KVL)ΣV(loop) = 0

    The virtual short means the loop from output through the feedback network back to the input must sum — that is what closed-loop gain really is.

  • Superposition theorem

    Summing and difference amplifiers are solved one input at a time with the others grounded, then added — superposition made practical.

  • Barkhausen criterion

    The condition to satisfy on purpose in a Wien-bridge oscillator, and to avoid by accident when a capacitive load causes ringing.

Each law is stated in full — with its diagram, variables and worked meaning — on the electrical laws page.

Markings

Part number printed on the IC. Pin 1 marked by a dot/notch.

Standard values

LM358/LM324 (cheap single-supply), TL071/TL072 (low-noise FET input), LM393 comparator, NE5532 (audio).

How to choose

Match supply (single vs dual), need rail-to-rail for low-voltage. Pick GBW >> your signal frequency x gain. Low offset for DC precision. Use a real comparator for compare jobs.

Pinout & package

1OFFSET8NC2IN−7V+3IN+6OUT4V−5OFFSET

DIP-8 — classic single op-amp (µA741) layout

Check first: Single op-amps (741) use this. Duals (LM358) and quads (LM324) share power on different pins — check the datasheet.

Single = 8-pin (out, in-, in+, V-, ..., V+). Dual/quad common. DIP-8, SOIC, SOT-23-5. Standard pinouts.

Example circuits

  • Non-inverting amplifier
  • Inverting amplifier / summing
  • Active low-pass filter
  • Voltage follower (buffer)
  • Comparator (better: use a comparator IC)

Common failures

Output stuck at a rail (wrong feedback, input out of range), oscillation (poor layout/decoupling), damage from over-voltage on inputs.

How to test

Power it, wire as a unity buffer, feed a known voltage - output should follow. Stuck at a rail with valid inputs = bad or mis-wired.

Substitutes

Pin-compatible part with equal/better GBW, slew, offset and matching supply type. TL072↔NE5532 for audio (check specs).

Where to buy

DigiKeyMouserLCSCRobuAmazon