The standard 8-pin operational amplifier pinout places Output A on Pin 1, Inverting Input A on Pin 2, Non-Inverting Input A on Pin 3, V- (Negative Supply) on Pin 4, Inverting Input B on Pin 6, Non-Inverting Input B on Pin 5, Output B on Pin 7, and V+ (Positive Supply) on Pin 8. This JEDEC-standard layout applies to the vast majority of dual op-amps (like the TL072 or NE5532) and single op-amps with offset null pins (like the LM741).
The Standard 8-Pin Op Amp Pinout Table
Before you wire up your breadboard or send your PCB to fab, verify your pin mapping against this reference. While the physical packages vary, the logical pinout for 8-pin op-amps has remained virtually unchanged for decades, standardized originally by Texas Instruments and adopted industry-wide.
| Pin # | Dual Op-Amp (e.g., TL072, NE5532, OPA2134) | Single w/ Offset Null (e.g., LM741) | Practical Function & Bench Notes |
|---|---|---|---|
| 1 | Output A | Offset Null | Dual: Drives the load for Channel A. Single: Connects to a 10kΩ trim pot wiper to nullify input offset voltage. |
| 2 | Inverting Input A (-) | Inverting Input (-) | The negative feedback node. High impedance; keep traces short to avoid parasitic capacitance and oscillation. |
| 3 | Non-Inverting Input A (+) | Non-Inverting Input (+) | The signal reference node. Often tied to a voltage divider for single-supply virtual ground biasing. |
| 4 | V- (Negative Supply / GND) | V- (Negative Supply / GND) | Most negative potential. In single-supply circuits, this is your system ground (0V). Add a 100nF decoupling cap to V+. |
| 5 | Non-Inverting Input B (+) | Offset Null | Dual: Signal reference for Channel B. Single: The other end of the offset null trim pot. |
| 6 | Inverting Input B (-) | Output | Dual: Negative feedback for Channel B. Single: The main output driver pin. |
| 7 | Output B | V+ (Positive Supply) | Dual: Drives the load for Channel B. Single: Most positive potential (e.g., +15V or +5V). |
| 8 | V+ (Positive Supply) | NC (No Connect) | Dual: Most positive potential. Single: Internally unconnected; do not use as a mechanical anchor or ground tie. |
Rows People Get Wrong (and How to Avoid Fried Silicon)
Even experienced builders make pinout assumptions that lead to dead ICs. Here are the specific rows and pins that cause the most bench failures.
Swapping V+ (Pin 8/7) and V- (Pin 4)
Reversing the power rails is the most common fatal error. Older op-amps like the LM741 lack internal reverse-polarity protection. If you swap V+ and V-, the internal substrate diodes become forward-biased, creating a dead short across your power supply. The IC will draw massive current, overheat in under two seconds, and the epoxy package can literally crack or vent hot plastic. Always verify power rails with a multimeter before inserting the chip.
Misusing Offset Null Pins (Pins 1 and 5 on Singles)
On single op-amps like the LM741, Pins 1 and 5 are strictly for offset voltage trimming. A common mistake is trying to use these as auxiliary signal inputs or tying them directly to ground. Tying them to ground can unbalance the internal differential pair, causing massive DC offset at the output. If you aren't actively trimming the offset, consult the specific datasheet—some modern Analog Devices op-amps require these pins to be left floating (NC), while others require them tied to V-.
Assuming NC (No Connect) Means "Ground"
On single 8-pin packages, Pin 8 is often marked as NC (No Connect). This does not mean it is internally tied to ground or that it is safe to use as a mechanical solder anchor. In high-vibration environments, soldering a ground wire to an NC pin can cause mechanical stress that cracks the silicon die inside the package.
Schematic Symbols and Package Standard Variants
While the logical pinout is universal, the way op-amps are represented on schematics and packaged in silicon varies by standard and region.
Schematic Symbol Variants: ANSI vs. IEC
In the US and most hobbyist literature, you will see the ANSI/IEEE 315 symbol: a triangle pointing to the right, with the non-inverting input marked with a plus (+) and the inverting input with a minus (-). However, in European industrial schematics and strict IEC-compliant documentation, you will encounter the IEC 60617 rectangular block symbol. The IEC symbol uses a rectangle with an internal infinity-like amplifier symbol (or a triangle inside the box). The pin functions remain identical, but the visual representation can confuse builders reading imported schematics.
Package Standards: DIP-8 vs. SOIC-8
The logical pinout is defined by JEDEC standards (specifically MS-001 for DIP). When moving from through-hole DIP-8 to surface-mount SOIC-8, the pin numbering sequence is identical: counter-clockwise starting from the notch/dot. However, the physical orientation trips people up. When a DIP chip is seated in a breadboard, you read it top-down. When soldering an SOIC chip to a PCB, you are looking at the top side, but the pins are bent outward. The "mirrored" confusion happens when builders look at the *bottom* of a DIP chip and try to map it directly to the *top* of an SOIC footprint. Always map pins based on the top-down view with the notch pointing left or up.
Safe Interpretation of Faded or Missing Markings
If you are scavenging parts or dealing with a laser-etched IC where the text has rubbed off, you can still safely identify the pinout. Look for physical package indicators: a molded dot near Pin 1, a chamfered (beveled) edge on the top left corner, or a semi-circular notch at the top. If all physical markers are gone, use the substrate diode trick: set your multimeter to diode test mode. Measure between suspected power pins and the input pins. The internal ESD protection diodes will typically show a ~0.6V forward voltage drop from the negative rail (Pin 4) to the inputs, and from the inputs to the positive rail (Pin 8). This allows you to definitively map the power rails without guessing.
Frequently Asked Questions
What do the offset null pins do on an op amp pinout?
Offset null pins (typically Pins 1 and 5 on single 8-pin op-amps) connect to the internal current mirrors of the input differential pair. Because of microscopic manufacturing variances, the two input transistors are never perfectly matched, resulting in a small DC voltage error (input offset voltage). By connecting a 10kΩ trimmer potentiometer between these two pins and tying the wiper to V-, you can manually inject a balancing current to force the output to exactly 0.00V when the inputs are shorted together. In modern precision op-amps (like chopper-stabilized types), internal laser trimming eliminates the need for these pins entirely.
How do I identify pin 1 on an op amp with completely faded markings?
First, inspect the physical package under a bright light or magnifying glass for a subtle indent dot, a mold ejector pin mark, or a chamfered edge on the plastic near Pin 1. If the package is completely smooth and unmarked, use a multimeter in diode-test mode. Probe the pins to find the power rails using the internal ESD protection diodes (expecting a ~0.6V drop between the negative rail and inputs). Once you identify V- (Pin 4) and V+ (Pin 8), Pin 1 is simply the pin at the opposite end of the notch/dot side, following the standard counter-clockwise JEDEC numbering sequence.
Are op amp pinouts universal across all manufacturers?
For standard 8-pin dual and single configurations, yes. A TL072 from Texas Instruments, an NE5532 from ON Semiconductor, and an OPA2134 from Burr-Brown all share the exact same DIP-8/SOIC-8 pinout. This industry standardization allows you to swap parts for upgrades (e.g., swapping a noisy JRC4558 for a low-noise OPA2134 in an audio pedal) without redesigning the PCB. However, this universality breaks down with quad op-amps (14-pin packages) or specialized instrumentation amplifiers, which have highly manufacturer-specific pinouts. Always verify via datasheets before swapping non-standard parts.
Why does my SOIC-8 op amp pinout look mirrored compared to the DIP-8?
It isn't actually mirrored; it is a matter of perspective. When you hold a through-hole DIP-8 chip in your hand, you look at the top. When you place a surface-mount SOIC-8 chip on a PCB, the pins bend down and away from you. If you accidentally flip the SOIC chip over to look at the "belly" side (where the solder joints are), the left-to-right order of the pins reverses relative to your eyes, making it look mirrored. To avoid soldering errors, always verify the SOIC footprint on your PCB silkscreen using the top-down view: the notch or dot indicates the top edge, and Pin 1 is always the top-left pad, counting counter-clockwise down the left side and back up the right.
