Where are the power pins on an LM324?

On the LM324 quad op-amp (DIP-14), VCC (V+) is on pin 4 and GND (V−) is on pin 11. This is the single most common LM324 wiring mistake: because beginners are used to the 8-pin LM358 putting power on the top-right corner (pin 8) and ground on the bottom-left corner (pin 4), they assume the 14-pin part follows the corners too. It does not — power and ground sit in the middle of the two long sides. Double-check against the LM324 pinout page before you wire it.

What is the difference between the LM358 and LM324?

They are essentially the same op-amp design, just packaged with a different number of amplifiers. The LM358 is a dual op-amp (two amplifiers) in a DIP-8, while the LM324 is a quad op-amp (four amplifiers) in a DIP-14. Each amplifier inside both parts uses the identical OUT / IN− / IN+ pin pattern, so once you can wire one channel of an LM358 you can wire any channel of an LM324. The only real gotcha is the power pins: LM358 uses pins 8 (V+) and 4 (V−), the LM324 uses pins 4 (V+) and 11 (V−).

Can an LM358 output reach the positive rail?

No. The LM358 and LM324 are single-supply op-amps whose inputs work down to the negative rail (ground), which makes them very convenient on a single 5V or 12V supply. But the output cannot swing all the way up to V+ — it typically falls a volt or more short of the positive rail — and near ground the output stage shows crossover distortion. For a true rail-to-rail output or a clean low-distortion signal, choose a rail-to-rail op-amp such as a TL072-class or a dedicated rail-to-rail part instead.

What are LM741 pins 1 and 5 for?

On the LM741 (DIP-8), pins 1 and 5 are the offset-null pins. To trim the input offset voltage you connect a small potentiometer (commonly 10kΩ) across pins 1 and 5 with its wiper going to V− (pin 4). Adjusting the pot nulls out the op-amp’s built-in offset for precision DC work. If you do not need offset trimming you can simply leave pins 1 and 5 unconnected — and note pin 8 is NC (no connection).

Op-Amp · Pinout · 7 min

Op-Amp Pinout & Basics: LM358 / LM324 / LM741, and the Two Core Circuits

Circflow Editorial · Published 2026-06-03

The first three op-amps almost every beginner meets are the LM358 (dual, DIP-8), the LM324 (quad, DIP-14) and the LM741 (single, DIP-8). Each amplifier inside them shares the same OUT / IN− / IN+ pattern, so the chips feel familiar — but the LM324 hides a trap: it puts V+ on pin 4 and V− on pin 11, not the corner pins you would expect from an 8-pin part. This guide gives the exact pinout of all three, explains the inverting and non-inverting inputs, walks the two core gain circuits with worked numbers, and is honest about the single-supply ground-swing limitation. Run the gain numbers in the Op-Amp Gain Calculator.

Pinout comparison table

Hold each DIP with the notch (or pin-1 dot) at the top; pin 1 is the top-left pin, and numbering runs down the left side and back up the right. With that single orientation the three parts compare like this:

Part	Package	Op-amps inside	V+ pin	V− / GND pin	Notable
LM358	DIP-8	2 (dual)	Pin 8	Pin 4	Standard dual pinout
LM324	DIP-14	4 (quad)	Pin 4	Pin 11	V+ / GND in the middle — the trap
LM741	DIP-8	1 (single)	Pin 7	Pin 4	Offset null on 1 & 5, pin 8 = NC

⚠️ The dual LM358 follows the standard dual pinout (V+ on pin 8, V− on pin 4). The quad LM324 does not use the corner pins — V+ is on pin 4 and V− on pin 11, in the middle of the long sides. The LM741 adds offset-null pins 1 & 5 and leaves pin 8 unconnected (NC).

LM358 dual op-amp (DIP-8)

The LM358 packs two independent op-amps into a DIP-8. Power sits on the standard corners — VCC (V+) on pin 8 (top-right) and GND (V−) on pin 4 (bottom-left). The two amplifiers wrap around the chip:

Pin	Function	Pin	Function
1	OUT1	5	IN2+
2	IN1−	6	IN2−
3	IN1+	7	OUT2
4	GND (V−)	8	VCC (V+)

So amplifier 1 lives on pins 1–3 (OUT1, IN1−, IN1+) and amplifier 2 on pins 5–7 (IN2+, IN2−, OUT2). Note that the per-amp order is OUT, IN−, IN+ — exactly the pattern the LM324 repeats four times.

LM324 quad op-amp (DIP-14) — the trap

The LM324 is the four-amplifier version in a DIP-14. Each channel uses the same OUT / IN− / IN+ pattern as the LM358, which is why the two parts feel interchangeable. The catch is the power pins:

Pin	Function	Pin	Function
1	OUT1	8	OUT3
2	IN1−	9	IN3−
3	IN1+	10	IN3+
4	VCC (V+)	11	GND (V−)
5	IN2+	12	IN4+
6	IN2−	13	IN4−
7	OUT2	14	OUT4

🛑 The classic LM324 mistake: power is on pin 4 (VCC / V+) and ground on pin 11 (GND / V−) — not the corner pins (1, 7, 8, 14) you would reach for out of LM358 habit. Wiring V+ to pin 14 or ground to pin 7 because "that’s where they were on the 8-pin chip" is the single most common LM324 wiring error. Confirm against the LM324 pinout page every time.

LM741 single op-amp (DIP-8)

The LM741 is the classic single op-amp in a DIP-8. Only one amplifier, but it spends two pins on offset trimming:

Pin	Function	Pin	Function
1	Offset null	5	Offset null
2	IN−	6	OUT
3	IN+	7	V+
4	V−	8	NC

The signal pins are IN− (pin 2), IN+ (pin 3) and OUT (pin 6), with power on V− (pin 4) and V+ (pin 7). Pins 1 and 5 are offset null — a trim pot across them (wiper to V−) cancels the input offset voltage for precision DC work. Pin 8 is NC (no connection). The offset-null detail on pins 1 & 5 is the LM741 fact beginners most often miss.

Reading the inputs: IN+ and IN−

Every op-amp has two inputs and one output. The non-inverting input (IN+) drives the output the same direction as the input — raise IN+ and the output rises. The inverting input (IN−) drives it the opposite way — raise IN− and the output falls. The amplifier works to make IN+ and IN− equal (the "virtual short" of an ideal op-amp with feedback).

LM358: amp 1 has IN1− on pin 2 and IN1+ on pin 3; amp 2 has IN2+ on pin 5 and IN2− on pin 6.
LM324: repeats the same per-amp order four times — e.g. amp 1 = OUT1/IN1−/IN1+ on pins 1/2/3, amp 4 = IN4+/IN4−/OUT4 on pins 12/13/14.
LM741: IN− on pin 2, IN+ on pin 3.

Because the LM358 and LM324 share the same OUT, IN−, IN+ grouping per channel, learning one teaches you both.

The two core circuits

With the pins sorted, almost every beginner op-amp project is one of two configurations. Both set their gain with just two resistors.

Non-inverting amplifier

The input goes to IN+, and a divider of Rf (feedback, OUT → IN−) and Rg (IN− → ground) sets the gain:

Vout = Vin × (1 + Rf / Rg)

Worked example: with Rf = 10k and Rg = 10k, gain = 1 + 10k/10k = 2, so a 1V input gives 2V out (same polarity). The gain is always ≥ 1. Size the divider with the Voltage Divider Calculator and check currents with the Ohm’s Law Calculator.

Inverting amplifier

The input goes through Rin to IN− (with IN+ at the reference, usually ground), and Rf feeds back from OUT to IN−:

Vout = −Vin × Rf / Rin

Worked example: with Rf = 10k and Rin = 1k, gain = −10k/1k = −10, so a 1V input gives −10V out (inverted polarity). The minus sign means the output is flipped. Drop your Rf / Rin (or Rf / Rg) values straight into the Op-Amp Gain Calculator to get the gain and output for either topology.

Single-supply gotcha

The LM358 and LM324 are popular precisely because they run from a single supply and their inputs work all the way down to the negative rail (ground) — no split ± supply needed. That is genuinely convenient for hobby and microcontroller projects.

🛑 Honest limitation: these are not rail-to-rail parts. The output cannot swing all the way up to V+ (it typically falls a volt or more short), and right near ground the output stage shows crossover distortion. For a true rail-to-rail output, a clean low-distortion audio signal, or precision work, reach for a rail-to-rail or low-distortion op-amp such as the TL072 class or a dedicated rail-to-rail part instead. Match the op-amp to the job rather than defaulting to the LM358/LM324 every time.

🛑 Pinouts and electrical figures here are reference values drawn from the manufacturer datasheets. Exact pin functions, swing limits, offset behavior and supply ranges vary by manufacturer and revision; for production, defer to the specific datasheet and revision for the part you actually buy.

FAQ

Where are the power pins on an LM324?: On the LM324 quad op-amp (DIP-14), VCC (V+) is on pin 4 and GND (V−) is on pin 11. This is the single most common LM324 wiring mistake: because beginners are used to the 8-pin LM358 putting power on the top-right corner (pin 8) and ground on the bottom-left corner (pin 4), they assume the 14-pin part follows the corners too. It does not — power and ground sit in the middle of the two long sides. Double-check against the LM324 pinout page before you wire it.
What is the difference between the LM358 and LM324?: They are essentially the same op-amp design, just packaged with a different number of amplifiers. The LM358 is a dual op-amp (two amplifiers) in a DIP-8, while the LM324 is a quad op-amp (four amplifiers) in a DIP-14. Each amplifier inside both parts uses the identical OUT / IN− / IN+ pin pattern, so once you can wire one channel of an LM358 you can wire any channel of an LM324. The only real gotcha is the power pins: LM358 uses pins 8 (V+) and 4 (V−), the LM324 uses pins 4 (V+) and 11 (V−).
Can an LM358 output reach the positive rail?: No. The LM358 and LM324 are single-supply op-amps whose inputs work down to the negative rail (ground), which makes them very convenient on a single 5V or 12V supply. But the output cannot swing all the way up to V+ — it typically falls a volt or more short of the positive rail — and near ground the output stage shows crossover distortion. For a true rail-to-rail output or a clean low-distortion signal, choose a rail-to-rail op-amp such as a TL072-class or a dedicated rail-to-rail part instead.
What are LM741 pins 1 and 5 for?: On the LM741 (DIP-8), pins 1 and 5 are the offset-null pins. To trim the input offset voltage you connect a small potentiometer (commonly 10kΩ) across pins 1 and 5 with its wiper going to V− (pin 4). Adjusting the pot nulls out the op-amp’s built-in offset for precision DC work. If you do not need offset trimming you can simply leave pins 1 and 5 unconnected — and note pin 8 is NC (no connection).