LM747 — Dual General-Purpose Operational Amplifier (Dual 741)

Overview

The LM747 (commonly LM747N or $\mu\text{A}747$ in a 14-pin DIP package) is a classic dual general-purpose operational amplifier IC manufactured by Texas Instruments, Fairchild, and National Semiconductor. It integrates two independent 741-type operational amplifiers on a single chip.

Each amplifier stage in the LM747 features short-circuit protection, internal frequency compensation, no latch-up under over-voltage, and dedicated Offset Null pins for precision DC voltage zeroing. It is popular in vintage analog audio, educational electronics, and legacy test gear repairs.

Quick reference


Op-Amp Type	Dual General-Purpose Operational Amplifier (Dual 741)
Package	14-Pin DIP (Through-Hole) / CDIP-14
Supply Voltage Range ( $V_{CC}$ )	$\pm 3.0\text{ V}$ to $\pm 18.0\text{ V}$ ( $6.0\text{ V}$ to $36.0\text{ V}$ single supply)
Gain Bandwidth Product (GBW)	$1.0\text{ MHz}$
Slew Rate	$0.5\text{ V}/\mu\text{s}$
Offset Nulling	Dedicated Offset Null pins for both amplifier channels
Short-Circuit Protection	Continuous output short-circuit protection to ground

Pinout (14-Pin DIP Package)

text

        ┌──────────────┐
   1IN- ─│ 1         14 │─ 1OFFSET NULL (a)
   1IN+ ─│ 2         13 │─ 1V+
 1OS(b) ─│ 3         12 │─ 1OUT
     V- ─│ 4         11 │─ N.C.
 2OS(b) ─│ 5         10 │─ 2OUT
   2IN+ ─│ 6          9 │─ 2V+
   2IN- ─│ 7          8 │─ 2OFFSET NULL (a)
        └──────────────┘

Pin	Name	Description
1	`1IN-`	Operational Amplifier 1 inverting input
2	`1IN+`	Operational Amplifier 1 non-inverting input
3	`1OFFSET NULL (b)`	Operational Amplifier 1 Offset Null pin b
4	`V-`	Common negative power supply rail ( $-15\text{V}$ for dual supply, $0\text{V}$ for single supply)
5	`2OFFSET NULL (b)`	Operational Amplifier 2 Offset Null pin b
6	`2IN+`	Operational Amplifier 2 non-inverting input
7	`2IN-`	Operational Amplifier 2 inverting input
8	`2OFFSET NULL (a)`	Operational Amplifier 2 Offset Null pin a
9	`2V+`	Operational Amplifier 2 positive supply rail
10	`2OUT`	Operational Amplifier 2 output pin
11	`N.C.`	No Connection
12	`1OUT`	Operational Amplifier 1 output pin
13	`1V+`	Operational Amplifier 1 positive supply rail
14	`1OFFSET NULL (a)`	Operational Amplifier 1 Offset Null pin a

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Supply Voltage Range	$V_{CC}$	$\pm 3.0$	$\pm 15$	$\pm 18$	V	Operational dual supply
Input Offset Voltage	$V_{IO}$	—	1.0	5.0	mV	$R_S \le 10\text{k}\Omega, T_A = 25^\circ\text{C}$
Input Bias Current	$I_{IB}$	—	80	500	nA
Large Signal Voltage Gain	$A_{VD}$	50	200	—	V/mV	$V_{CC} = \pm 15\text{V}, R_L \ge 2\text{k}\Omega$
Slew Rate	$SR$	—	0.5	—	$\text{V}/\mu\text{s}$
Supply Current	$I_{CC}$	—	3.4	5.6	mA	Both amplifiers ( $I_O = 0$ )

Common mistakes

Confusing 14-pin LM747 pinout with 8-pin dual op-amps: Unlike modern dual op-amps (like LM358 or TL072 which use an 8-pin footprint), the LM747 uses a 14-pin DIP footprint with separate positive supply pins (1V+ and 2V+) and offset null pins.
Single-supply operation near GND: The 741 topology does not feature a ground-sensing input stage. When operated on a single supply (e.g. $+15\text{V}$ to $0\text{V}$ ), inputs must be biased to at least $+3.0\text{ V}$ above GND.

Notes

Dual 741 Legacy: The LM747 is effectively two 741 op-amps in one 14-pin IC, sharing only the common negative supply pin (Pin 4: V-).

Interface	Dual Op-Amp Terminals (1IN+, 1IN-, 1OUT, 2IN+, 2IN-, 2OUT), Dual Offset Null Pins
Package	14-pin PDIP / CDIP-14