OP27GS(2002) 查看數據表（PDF） - Analog Devices

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OP27GS
(Rev.:2002)

Low Noise, Precision Operational Amplifier

Analog Devices 

0.1␮F

100k⍀

OP27

10⍀ D.U.T.

2k⍀

VOLTAGE

GAIN

= 50,000

4.7␮F

OP12

100k⍀

4.3k⍀ 22␮F

SCOPE ؋ 1

RIN = 1M⍀

0.1␮F 2.2␮F

24.3k⍀

110k⍀

2.4

TA = 25؇C

2.2 VS = ؎15V

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

100

1k

10k

LOAD RESISTANCE – ⍀

100k

TPC 28. Voltage Noise Test Circuit

(0.1 Hz to 10 Hz)

TPC 29. Open-Loop Voltage Gain vs.

Load Resistance

160

TA = 25؇C

140

120

100

80

NEGATIVE

SWING

60

POSITIVE

40

SWING

20

0

1 10 100 1k 10k 100k 1M 10M 100M

FREQUENCY – Hz

TPC 31. PSRR vs. Frequency

OP27

120

80

40

0

–40

–90

–120

1 SEC/DIV

0.1Hz to 10Hz p-p NOISE

TPC 30. Low-Frequency Noise

APPLICATION INFORMATION

OP27 series units may be inserted directly into 725 and OP07

sockets with or without removal of external compensation or

nulling components. Additionally, the OP27 may be fitted to

unnulled 741-type sockets; however, if conventional 741 nulling

circuitry is in use, it should be modified or removed to ensure

correct OP27 operation. OP27 offset voltage may be nulled to

zero (or another desired setting) using a potentiometer (see

Offset Nulling Circuit).

The OP27 provides stable operation with load capacitances of

up to 2000 pF and ± 10 V swings; larger capacitances should be

decoupled with a 50 Ω resistor inside the feedback loop. The

OP27 is unity-gain stable.

Thermoelectric voltages generated by dissimilar metals at the

input terminal contacts can degrade the drift performance. Best

operation will be obtained when both input contacts are main-

tained at the same temperature.

OFFSET VOLTAGE ADJUSTMENT

The input offset voltage of the OP27 is trimmed at wafer level.

However, if further adjustment of VOS is necessary, a 10 kΩ trim

potentiometer can be used. TCVOS is not degraded (see Offset

Nulling Circuit). Other potentiometer values from 1 kΩ to 1 MΩ

can be used with a slight degradation (0.1 µV/°C to 0.2 µV/°C)

of TCVOS. Trimming to a value other than zero creates a drift of

approximately (VOS/300) µV/°C. For example, the change in

TCVOS will be 0.33 µV/°C if VOS is adjusted to 100 µV. The

offset voltage adjustment range with a 10 kΩ potentiometer is

± 4 mV. If smaller adjustment range is required, the nulling

sensitivity can be reduced by using a smaller pot in conjuction

with fixed resistors. For example, the network below will have a

± 280 µV adjustment range.

1

4.7k⍀ 1k⍀ POT 4.7k⍀

8

V+

Figure 2.

NOISE MEASUREMENTS

To measure the 80 nV peak-to-peak noise specification of the

OP27 in the 0.1 Hz to 10 Hz range, the following precautions

must be observed:

1. The device must be warmed up for at least five minutes.

As shown in the warm-up drift curve, the offset voltage

typically changes 4 µV due to increasing chip temperature

after power-up. In the 10-second measurement interval,

these temperature-induced effects can exceed tens-of-

nanovolts.

2. For similar reasons, the device has to be well-shielded from

air currents. Shielding minimizes thermocouple effects.

REV. A

–11–

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