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 amp’s 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
= 600Ω
Worst case sine
wave R
L
= 600Ω
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) 50kΩ to 1MΩ
Trim Potentiometer
(100kΩ Recommended)
+V
CC
–V
CC
7
6
5
1
(1)
4
3
2
