LM358 Dual Op-Amp Pinout
DIP-8 package, top view, pin 1 at the notch. Check your board against its silkscreen before wiring power.
What the two op-amps share
Both amplifiers sit in one package and share a single supply and a single ground, so a fault on one side pulls the other with it. They do not share inputs or outputs. If half the chip is unused, do not leave it floating: wire it as a unity-gain follower with its input tied to a mid-supply reference, or its output will slam against a rail and add noise to the half you care about.
Single supply, and what that costs
The LM358 works from a single supply, which is why it appears in so many hobby circuits, but its output cannot reach either rail. Expect it to swing to within about 1.5 V of the positive rail and close to, though not exactly, ground. On a 5 V supply that leaves roughly 0 to 3.5 V of usable output. If a circuit needs the output to reach 5 V, the part to reach for is a rail-to-rail op-amp such as the MCP6002, not the LM358.
Two amplifiers, one supply
The LM358 holds two independent op-amps sharing the power pins. It was designed for single-supply use from 3 to 32 V, and its inputs work down to ground, which is why it appears in so many sensor circuits.
Know its limits
The output cannot swing closer than roughly 1.5 V to the positive rail, and it is slow by modern standards. For audio or precision work it is the part you prototype with and then replace; for comparators, thresholds and battery projects it is exactly right.
Sources and datasheets
This diagram was cross-checked against the manufacturer documentation below plus at least two independent references before publishing. When they disagreed, the manufacturer won.
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