Datasheet

8
®
OPA134/2134/4134
APPLICATIONS INFORMATION
OPA134 series op amps are unity-gain stable and suitable
for a wide range of audio and general-purpose applications.
All circuitry is completely independent in the dual version,
assuring normal behavior when one amplifier in a package
is overdriven or short-circuited. Power supply pins should
be bypassed with 10nF ceramic capacitors or larger to
minimize power supply noise.
OPERATING VOLTAGE
OPA134 series op amps operate with power supplies from
±2.5V to ±18V with excellent performance. Although
specifications are production tested with ±15V supplies,
most behavior remains unchanged throughout the full
operating voltage range. Parameters which vary signifi-
cantly with operating voltage are shown in the typical
performance curves.
OFFSET VOLTAGE TRIM
Offset voltage of OPA134 series amplifiers is laser trimmed
and usually requires no user adjustment. The OPA134
(single op amp version) provides offset trim connections
on pins 1 and 8, identical to 5534 amplifiers. Offset
voltage can be adjusted by connecting a potentiometer as
shown in Figure 1. This adjustment should be used only to
null the offset of the op amp, not to adjust system offset or
offset produced by the signal source. Nulling offset could
change the offset voltage drift behavior of the op amp.
While it is not possible to predict the exact change in drift,
the effect is usually small.
TOTAL HARMONIC DISTORTION
OPA134 series op amps have excellent distortion character-
istics. THD+Noise is below 0.0004% throughout the audio
frequency range, 20Hz to 20kHz, with a 2kΩ load. In
addition, distortion remains relatively flat through its
wide output voltage swing range, providing increased head-
room compared to other audio amplifiers, including the
OP176/275.
FIGURE 1. OPA134 Offset Voltage Trim Circuit.
V+
V–
100kΩ
OPA134 single op amp only. 
Use offset adjust pins only to null
offset voltage of op amp—see text.
Trim Range: ±4mV typ
OPA134
6
7
8
4
3
2
1
10nF
10nF
In many ways headroom is a subjective measurement. It can
be thought of as the maximum output amplitude allowed
while still maintaining a very low level of distortion. In an
attempt to quantify headroom, we have defined “very low
distortion” as 0.01%. Headroom is expressed as a ratio
which compares the maximum allowable output voltage
level to a standard output level (1mW into 600Ω, or
0.7746Vrms). Therefore, OPA134 series op amps, which
have a maximum allowable output voltage level of 11.7Vrms
(THD+Noise < 0.01%), have a headroom specification of
23.6dBu. See the typical curve “Headroom - Total Harmonic
Distortion + Noise vs Output Amplitude.”
DISTORTION MEASUREMENTS
The distortion produced by OPA134 series op amps is below
the measurement limit of all known commercially available
equipment. However, a special test circuit can be used to
extend the measurement capabilities.
Op amp distortion can be considered an internal error source
which can be referred to the input. Figure 2 shows a
circuit which causes the op amp distortion to be 101 times
greater than normally produced by the op amp. The addition
of R
3
to the otherwise standard non-inverting amplifier
FIGURE 2. Distortion Test Circuit.
R
2
OPA134
R
1
Signal Gain = 1+
Distortion Gain = 1+
R
3 V
O
= 3Vrms
Generator
Output
Analyzer
Input
Audio Precision
System One
Analyzer
(1)
R
L

1kΩ
IBM PC
or
Compatible
SIG.
GAIN
DIST.
GAIN
R
1
R
2
R
3
∞
100Ω
10Ω
1kΩ
1kΩ
1kΩ
10Ω
11Ω
∞
1
11
101
101
101
101
NOTE: (1) Measurement BW = 80kHz
R
2
R
1
R
2
R
1
II R
3