Op Amp Symbol Explained: Pinout, Polarity, and Power Pins

Published Jun 22, 2026, updated Jun 22, 2026

9 min

What is the Symbol of an Operational Amplifier?
How to Read an Op Amp Symbol in a Schematic
Common Mistakes When Reading Op Amp Symbol
Op Amp Symbol Inverting vs Non-Inverting Input
Understanding Op Amp Power Supply Pins
Op Amp vs Comparator Symbol
741 Op Amp Pinout: Mapping the Symbol to Real Pins
From Op Amp Schematic Symbol to PCB Footprint
FAQs about Op Amp Symbol
Conclusion

The op amp symbol is one of the most common shapes in analog schematics: a triangle with two inputs and one output. Reading it correctly, knowing which pin is inverting, which is non-inverting, and how power connects, is the first skill needed before building any amplifier circuit.

Standard op amp symbols include a non-inverting input, an inverting input, an output, and power supply connections that may be shown or hidden depending on schematic style. The common symbol convention uses a triangle with labeled inputs and output.

What You'll Learn in This Guide

What each part of the op amp symbol means
Why inputs are marked + and −, and what that controls
How power supply pins work, and why they're often hidden
How to spot voltage follower, inverting amp, and comparator circuits
How the op amp symbol differs from the comparator symbol
How to map the 741 symbol to its real DIP-8 pinout
How schematic symbols connect to PCB footprints

What is the Symbol of an Operational Amplifier?

An operational amplifier symbol represents a high-gain differential amplifier. It is drawn as a triangle, with the flat side on the left (inputs) and the point on the right (output), showing signal flow direction.

The Three Main Connections

Every op amp symbol has three core terminals:

Non-inverting input (+)
Inverting input (−)
Output

Figure: Op amp symbol diagram showing inverting input, non-inverting input, and output

Operational Amplifier Symbol Quick Reference

Marking	Meaning
+	Non-inverting input
−	Inverting input
Output	Amplified signal
VS+	Positive supply
VS−	Negative supply

Symbol Element	Function
Triangle shape	Represents amplifier, signal flows left to right
+ terminal	Non-inverting input
− terminal	Inverting input
Tip of triangle	Output (Vout)
Vertical lines (if shown)	Power supply rails, VS+ and VS−

How to Read an Op Amp Symbol in a Schematic

Theory aside, most engineers need to recognize the symbol fast inside a real circuit. Three configurations cover almost every case a designer will encounter early on.

Example 1: Voltage Follower

Output feeds directly back to the inverting input. No gain, used as a buffer for high impedance sources.

Example 2: Inverting Amplifier

Input signal connects through a resistor to the inverting input. A feedback resistor, which you can read about in our resistor symbol guide, sets the gain. Non-inverting input is grounded.

Example 3: Comparator Circuit

One input is a fixed reference voltage, the other is the signal. No feedback path. Output swings between supply rails based on which input is higher.

In all three, the same triangle symbol appears; only the connections change, which is why context matters more than the shape itself.

Figure: Op amp schematic examples showing voltage follower, inverting amplifier, and comparator wiring

Common Mistakes When Reading Op Amp Symbol

Mistake	Fix
Assuming no power pins means no power needed	Always check datasheet for VS+ / VS− or +V/Gnd
Confusing op amp with comparator by shape alone	Check for feedback path, not just symbol shape
Swapping inverting and non-inverting pins when reading from datasheet vs textbook	Confirm pin numbers against the specific package, not memory
Ignoring single-supply limitations	Check output swing range before assuming dual-rail behavior

Op Amp Symbol Inverting vs Non-Inverting Input

The + and − marks on the input pins are the most important detail on the symbol. They determine output phase, not voltage polarity.

The Inverting Input (−)

A signal applied to the inverting input produces an output 180° out of phase. Positive input voltage swing produces negative output swing, relative to the reference point.

The Non-Inverting Input (+)

A signal applied to the non-inverting input produces an output in phase with the input. No phase flip occurs.

What the Plus and Minus Signs Really Mean in Op Amp

The signs do not indicate DC polarity or voltage level. They indicate which input path causes phase inversion at the output. This is a common point of confusion for new designers.

Equation:

Vout = A * (V+ − V−)

Where A is open loop gain, V+ is the non-inverting input voltage, and V− is the inverting input voltage.

Figure: Op amp symbol showing signal path from inverting and non-inverting inputs to output with phase result

Input	Sign	Output Phase	Typical Use
Non-inverting	+	In phase	Voltage follower, non-inverting amp
Inverting	−	180° out of phase	Inverting amp, summing circuit

Understanding Op Amp Power Supply Pins

Power pins are the most overlooked part of the op amp symbol, and the most common source of confusion when reading real schematics.

VS+ and VS− in Operational Amplifier

VS+ and VS− are the supply rails that power the op amp internally. They are separate from the signal inputs and output.

Without these connections, the op amp cannot operate, regardless of how the signal pins are wired. In practical designs, adding a bypass capacitor in PCB layout close to these supply lines is essential to filter out power supply noise.

Single-Supply vs Dual-Supply Op Amps

Dual-supply op amps use a positive and negative rail (for example +15V and −15V), allowing output swing above and below ground.
Single-supply op amps use +V and Gnd (or 0V), common in battery-powered and automotive designs, but limit output swing to the positive range.

Why Power Pins Are Often Hidden

In simplified schematics, especially in textbooks and tutorials, VS+ and VS− are frequently omitted to reduce clutter when the supply is implied or covered elsewhere in the design.

Always verify power pin connections against the datasheet before assuming a schematic is complete.

Figure: Three op amp symbols comparing hidden power pins, explicit VS+ VS- rails, and single-supply configuration

Configuration	Pins Used	Typical Application
Dual supply	VS+, VS−	Audio, instrumentation, precision analog
Single supply	+V, Gnd	Battery powered, automotive, sensors
Hidden rails	Implied, not drawn	Simplified teaching diagrams

Op Amp vs Comparator Symbol

Comparator and op-amp diagrams often use the same triangle symbol, which makes circuit context and feedback connections the key distinction, not the symbol shape.

Feature	Op Amp	Comparator
Symbol	Triangle	Triangle (often identical)
Operating mode	Linear, with feedback	Saturated, output at rail levels
Feedback	Usually present	Usually absent
Output behavior	Proportional to input difference	Binary high or low

Figure: Comparison of op amp symbol and comparator symbol showing the feedback path versus reference voltage input

741 Op Amp Pinout: Mapping the Symbol to Real Pins

Understanding the Classic 741 Op Amp Pinout

The 741 remains the most recognized educational op amp. Its classic DIP-8 pinout includes inverting input, non-inverting input, output, and positive and negative supply pins, plus offset null pins not required for basic use.

Mapping 741 Op Amp Symbol Pins to Physical Pins

The schematic symbol shows function (+ input, − input, output). The physical IC pinout shows location. Both must be cross-referenced when wiring a real board, since pin numbers vary by manufacturer and package type.

Figure: 741 op amp DIP-8 package top view showing pin 2 inverting input, pin 3 non-inverting input, pin 4 negative supply, pin 6 output, pin 7 positive supply

Pin	Name	Function
2	Inverting Input	(−)
3	Non-Inverting Input	(+)
4	V−	Negative Supply
6	Output	Amplified Signal
7	V+	Positive Supply

From Op Amp Schematic Symbol to PCB Footprint

Schematic vs. Footprint: The schematic symbol defines the component's function (inverting/non-inverting inputs, output), while the PCB footprint dictates the physical package (pin spacing, pad size, and orientation).
Preventing Errors: Pin orders must match exactly between the schematic and the footprint. Mismatched mappings often escape simulation checks and are only discovered after fabrication, which is costly and difficult to fix.
Verification: Before fabrication, verify three key elements: schematic symbol pin labels, footprint pin assignments, and the actual package pinout from the datasheet.
Package Switching: Always verify pin configurations when changing package types (e.g., from through-hole DIP-8 to surface-mount SOIC-8), as physical spacing and pin orientation often differ even if the pin count remains the same.

Figure: Showing progression from op amp schematic symbol to DIP-8 footprint to assembled PCB

FAQs about Op Amp Symbol

Q: How do you identify Pin 1 on physical DIP-8 and SOIC-8 op amp packages?

On standard DIP-8 and SOIC-8 packages, a small notch on one end of the plastic body or a circular dot adjacent to a corner indicates Pin 1. Pin numbering always runs counter-clockwise starting from Pin 1 when looking at the package from the top down.

Q: What is the typical input impedance of an ideal operational amplifier?

An ideal op amp has infinite input impedance, meaning it draws zero current from the input signal source. In real-world circuits, this prevents the amplifier from loading down the preceding circuit stage.

Q: What are the offset null pins on the 741 op amp used for?

The offset null pins (typically pins 1 and 5 on the 741 DIP-8 package) are used to nullify small, unwanted DC voltage offsets between the inputs. A potentiometer can be connected across them to balance the internal differential amplifier stage.

Q: Why do some multi-channel op amp packages share a single schematic designator prefix?

Multi-channel ICs (such as dual or quad op amps) are represented as individual schematic gates (labeled U1A, U1B, etc.) to keep layout paths readable. These gates share a single designator prefix because they exist inside a single physical integrated circuit package.

Q: What happens if the positive and negative power supplies are connected in reverse?

Reversing the power supply connections forward-biases the internal ESD protection diodes and substrate junctions. This usually results in immediate, catastrophic thermal runaway and permanent silicon damage, rendering the IC unusable.

Conclusion

The op amp symbol looks simple, a triangle with two inputs and one output, but misreading the + and − pins or missing power connections causes real circuit errors. Knowing inverting vs non-inverting behavior, recognizing hidden power pins, and distinguishing op amps from comparators covers most real-world schematic reading needs. The 741 pinout example bridges symbol theory to physical wiring. Once the symbol is clear, moving from schematic to footprint to a working board becomes a much shorter step.