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
Key specs
Supply voltage
VSingle or dual rails; check it covers your signal range.
Gain-bandwidth product (GBW)
MHzTrade-off between gain and bandwidth.
Slew rate
V/µsHow fast the output can change.
Input offset voltage
mVTiny built-in error; lower = more precise.
Rail-to-rail?
-Whether in/out can swing to the supply rails.
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
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).