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OPA604AP

Part # OPA604AP
Description FET INPUT AUDIO OP AMP - Rail/Tube
Category IC
Availability In Stock
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Qty Price
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Burr-Brown Corporation
Date Code: 9241
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.

OPA604
7
SBOS019A
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
T
A
= +25°C, V
S
= ±15V, unless otherwise noted.
APPLICATIONS INFORMATION
OFFSET VOLTAGE ADJUSTMENT
The OPA604 offset voltage is laser-trimmed and will require
no further trim for most applications. As with most amplifiers,
externally trimming the remaining offset can change drift
performance by about 0.3µV/°C for each 100µV of adjusted
offset. The OPA604 can replace many other amplifiers by
leaving the external null circuit unconnected.
The OPA604 is unity-gain stable, making it easy to use in a
wide range of circuitry. Applications with noisy or high imped-
ance power supply lines may require decoupling capacitors
close to the device pins. In most cases, a 1µF tantalum
capacitor at each power supply pin is adequate.
DISTORTION MEASUREMENTS
The distortion produced by the OPA604 is below the mea-
surement limit of virtually all commercially available equip-
ment. A special test circuit, however, 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 noninverting amplifier configuration
alters the feedback factor or noise gain of the circuit. The
closed-loop gain is unchanged, but the feedback available
for error correction is reduced by a factor of 101. This
extends the measurement limit, including the effects of the
signal-source purity, by a factor of 101. Note that the input
signal and load applied to the op amp are the same as with
conventional feedback without R
3
.
Validity of this technique can be verified by duplicating
measurements at high gain and/or high frequency where the
distortion is within the measurement capability of the test
equipment. Measurements for this data sheet were made
with the Audio Precision System One, which greatly simpli-
fies such repetitive measurements. The measurement tech-
nique can, however, be performed with manual distortion
measurement instruments.
CAPACITIVE LOADS
The dynamic characteristics of the OPA604 have been
optimized for commonly encountered gains, loads and oper-
ating conditions. The combination of low closed-loop gain
and capacitive load will decrease the phase margin and may
lead to gain peaking or oscillations. Load capacitance reacts
with the op amps open-loop output resistance to form an
additional pole in the feedback loop. Figure 3 shows various
circuits which preserve phase margin with capacitive load.
For details of analysis techniques and applications circuits,
refer to application bulletin AB-028 (SBOA015) located at
www.ti.com.
FIGURE 1. Offset Voltage Trim.
Supply Voltage, ±V
S
(V)
6 8 10 12 14 16 18 20 22 24
0.5
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
Power Dissipation (W)
POWER DISSIPATION vs SUPPLY VOLTAGE
No signal
or no load
Typical high-level
music R
L
= 600
Worst case sine
wave R
L
= 600
Ambient Temperature (°C)
0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
Total Power Dissipation (W)
MAXIMUM POWER DISSIPATION vs TEMPERATURE
25 50 75 100 125 150
J-A
= 90°C/W
Soldered to
Circuit Board
(see text)
θ
Maximum
Specified Operating
Temperature
85°C
OPA604
±50mV Typical
Trim Range
NOTE: (1) 50k to 1M
Trim Potentiometer
(100k Recommended)
+V
CC
V
CC
7
6
5
1
(1)
4
3
2
OPA604
8
SBOS019A
www.ti.com
For the unity-gain buffer, Figure 3a, stability is preserved by
adding a phase-lead network, R
C
and C
C
. Voltage drop
across R
C
will reduce output voltage swing with heavy loads.
An alternate circuit, Figure 3b, does not limit the output with
low load impedance. It provides a small amount of positive
feedback to reduce the net feedback factor. Input impedance
of this circuit falls at high frequency as op amp gain rolloff
reduces the bootstrap action on the compensation network.
Figures 3c and 3d show compensation techniques for
noninverting amplifiers. Like the follower circuits, the circuit in
Figure 3d eliminates voltage drop due to load current, but at
the penalty of somewhat reduced input impedance at high
frequency.
Figures 3e and 3f show input lead compensation networks
for inverting and difference amplifier configurations.
NOISE PERFORMANCE
Op amp noise is described by two parametersnoise volt-
age and noise current. The voltage noise determines the
noise performance with low source impedance. Low noise
bipolar-input op amps such as the OPA27 and OPA37
provide very low voltage noise. But if source impedance is
greater than a few thousand ohms, the current noise of
bipolar-input op amps react with the source impedance and
will dominate. At a few thousand ohms source impedance
and above, the OPA604 will generally provide lower noise.
POWER DISSIPATION
The OPA604 is capable of driving a 600 load with power-
supply voltages up to ±24V. Internal power dissipation is
increased when operating at high power supply voltage. The
typical characteristic curve, Power Dissipation vs Power
Supply Voltage, shows quiescent dissipation (no signal or no
load) as well as dissipation with a worst case continuous sine
wave. Continuous high-level music signals typically produce
dissipation significantly less than worst-case sine waves.
Copper leadframe construction used in the OPA604 im-
proves heat dissipation compared to conventional plastic
packages. To achieve best heat dissipation, solder the de-
vice directly to the circuit board and use wide circuit board
traces.
OUTPUT CURRENT LIMIT
Output current is limited by internal circuitry to approximately
±40mA at 25°C. The limit current decreases with increasing
temperature as shown in the typical curves.
FIGURE 2. Distortion Test Circuit.
R
2
OPA604
R
1
R
3
V
O
= 10Vp-p
(3.5Vrms)
Generator
Output
Analyzer
Input
Audio Precision
System One
Analyzer
(1)
R
L
1k
IBM PC
or
Compatible
SIG.
GAIN
DIST.
GAIN
R
1
R
2
R
3
500
50
5k
5k
5k
50
500
1
10
100
101
101
101
NOTE: (1) Measurement BW = 80kHz
OPA604
9
SBOS019A
www.ti.com
FIGURE 3. Driving Large Capacitive Loads.
NOTE: Design equations and component values are approximate. User adjustment is required for optimum performance.
C
C
820pF
R
C
750
C
L
5000pF
e
i
C
C
= 120 X 10
12
C
L
(a)
e
o
C
L
5000pF
e
i
R
C
=
(b)
R
C
10
C
C
0.47µF
R
2
2k
R
2
4C
L
X 10
10
1
C
C
=
C
L
X 10
3
R
C
e
o
C
L
5000pF
R
2
10k
R
1
10k
C
C
=
50
R
2
C
L
e
i
R
C
25
C
C
24pF
(c)
e
o
C
L
5000pF
R
2
2k
R
1
2k
e
i
R
C
20
C
C
0.22µF
(d)
R
C
=
R
2
2C
L
X 10
10
(1 + R
2
/R
1
)
e
o
C
L
5000pF
R
2
2k
R
1
2k
e
i
R
C
20
C
C
0.22µF
(e)
R
C
=
R
2
2C
L
X 10
10
(1 + R
2
/R
1
)
e
o
C
L
5000pF
R
2
2k
R
1
2k
e
1
R
C
20
C
C
0.22µF
(f)
R
C
=
R
2
2C
L
X 10
10
(1 + R
2
/R
1
)
R
3
2k
e
2
R
4
2k
e
o
OPA604
C
C
=
C
L
X 10
3
R
C
C
C
=
C
L
X 10
3
R
C
C
C
=
C
L
X 10
3
R
C
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