NJM2068 — Low-Noise High-Slew-Rate Dual Audio Operational Amplifier

Overview

The NJM2068 (commonly NJM2068D in an 8-pin DIP package) is a low-noise, high-slew-rate dual operational amplifier manufactured by New Japan Radio (NJR / Nisshinbo Micro Devices). Designed specifically for audio preamplifiers, active equalizer networks, and mixing consoles, it offers superior noise performance compared to classic 4558 and 072 op-amps.

Featuring an equivalent input noise voltage of $0.44\ \mu\text{Vrms}$ , a gain-bandwidth product of $27\text{ MHz}$ , and a slew rate of $6.0\text{ V}/\mu\text{s}$ , the NJM2068 is widely deployed in commercial audio equipment and DIY audio preamps.

Quick reference


Op-Amp Type	Low-Noise High-Slew-Rate Dual Audio Operational Amplifier
Package	8-Pin DIP (Through-Hole) / DMP-8 / SSOP-8
Supply Voltage Range ( $V_{CC}$ )	$\pm 4.0\text{ V}$ to $\pm 18.0\text{ V}$ ( $8.0\text{ V}$ to $36.0\text{ V}$ single supply)
Equivalent Input Noise Voltage	$0.44\ \mu\text{Vrms}$ typical ( $R_S = 2.2\text{k}\Omega$ , RIAA filter)
Gain Bandwidth Product (GBW)	$27\text{ MHz}$ (at $f = 10\text{kHz}$ ) / $19\text{ MHz}$ unity gain
Slew Rate	$6.0\text{ V}/\mu\text{s}$
THD	$0.001\%$ typical ( $f = 1\text{kHz}, V_O = 5\text{Vrms}$ )

Pinout (Standard Dual Op-Amp 8-Pin Package)

text

        ┌──────────┐
  A OUT ─│ 1      8 │─ V+
  A -IN ─│ 2      7 │─ B OUT
  A +IN ─│ 3      6 │─ B -IN
     V- ─│ 4      5 │─ B +IN
        └──────────┘

Pin	Name	Description
1	`A OUTPUT`	Operational Amplifier A output
2	`A -INPUT`	Operational Amplifier A inverting input
3	`A +INPUT`	Operational Amplifier A non-inverting input
4	`V-` / `GND`	Negative power supply rail ( $-15\text{V}$ for dual supply, $0\text{V}$ for single supply)
5	`B +INPUT`	Operational Amplifier B non-inverting input
6	`B -INPUT`	Operational Amplifier B inverting input
7	`B OUTPUT`	Operational Amplifier B output
8	`V+`	Positive power supply rail ( $+15\text{V}$ for dual supply)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Supply Voltage Range	$V^+/V^-$	$\pm 4.0$	$\pm 15$	$\pm 18$	V	Dual supply range
Input Offset Voltage	$V_{IO}$	—	0.3	3.0	mV	$R_S \le 10\text{k}\Omega$
Input Bias Current	$I_{IB}$	—	150	500	nA
Equivalent Input Noise	$V_{NI}$	—	0.44	—	$\mu\text{Vrms}$	$R_S = 2.2\text{k}\Omega$ , RIAA filter
Slew Rate	$SR$	—	6.0	—	$\text{V}/\mu\text{s}$	$R_L \ge 2\text{k}\Omega$
Gain Bandwidth Product	$GBW$	—	27	—	MHz	$f = 10\text{kHz}$
Operating Current	$I_{CC}$	—	5.0	7.0	mA	Both channels ( $I_O = 0$ )

Common mistakes

Operating below 8V total supply: The NJM2068 requires at least $\pm 4.0\text{ V}$ ( $\ge 8.0\text{ V}$ single supply) for full internal biasing. Running off a 5V single supply causes severe distortion.
High source impedance noise: Because the NJM2068 uses BJT input transistors, its input bias currents can generate voltage noise across high-resistance feedback networks ( $>100\text{k}\Omega$ ). Keep feedback resistors below $10\text{k}\Omega$ for best noise performance.

Notes

NJM2068 vs RC4558: The NJM2068 offers 6x higher slew rate ( $6\text{V}/\mu\text{s}$ vs $1\text{V}/\mu\text{s}$ ) and 9x higher bandwidth ( $27\text{MHz}$ vs $3\text{MHz}$ ) than standard 4558 dual op-amps.

Interface	Dual Op-Amp Terminals (A -INPUT, A +INPUT, A OUTPUT, B -INPUT, B +INPUT, B OUTPUT)
Package	8-pin DIP / DMP-8 / SSOP-8