OPA604AP datasheet(7/16 Pages) TI

7 / 16 page

OPA604

SBOS019A

www.ti.com

TYPICAL CHARACTERISTICS (Cont.)

A = +25°C, VS = ±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 0.3

µV/°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 1

µF 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 R3 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 R3.

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)

0.5

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

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)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

MAXIMUM POWER DISSIPATION vs TEMPERATURE

100

125

150

J-A = 90°C/W

Soldered to

Circuit Board

(see text)

Maximum

Specified Operating

Temperature

85°C

OPA604

±50mV Typical

Trim Range

NOTE: (1) 50k

Ω to 1MΩ

Trim Potentiometer

(100k

Ω Recommended)

–V

(1)

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