7

LT1001

0.1Hz to 10Hz Noise Test Circuit

Offset Voltage Adjustment

The input offset voltage of the LT1001, and its drift with tempera-

ture, are permanently trimmed at wafer test to a low level.

However, if further adjustment of Vos is necessary, nulling with

a 10k or 20k potentiometer will not degrade drift with tempera-

ture. Trimming to a value other than zero creates a drift of (Vos/

300)

µV/°C, e.g., if Vos is adjusted to 300 µV, the change in drift

will be 1

µV/°C. The adjustment range with a 10k or 20k pot is

approximately

±2.5mV. If less adjustment range is needed, the

sensitivity and resolution of the nulling can be improved by using

a smaller pot in conjunction with fixed resistors. The example

below has an approximate null range of

±100 µV.

LT1001

–

+

LT1001

100k

Ω

2k

Ω

100k

4.3k

110k

SCOPE

× 1

0.1

µF

4.7

µF

24.3k

10

Ω

1001 F03

0.1

µF

22

µF

VOLTAGE GAIN = 50,000

2.2

µF

DEVICE

UNDER

TEST

Improved Sensitivity Adjustment

–15V

LT1001

+15V

2

3

7

6

OUTPUT

INPUT

1001 F02

4

8

7.5k

1k

7.5k

1

(Peak-to-Peak noise measured in 10 sec interval)

The device under test should be warmed up for three minutes and

shielded from air currents.

1001 F04

–

+

+

+–

+

2.2

µF

TANTALUM

INPUT

1k

30k

3.9k

30k

390

Ω

1.2k

.5

Ω

.5

Ω

470

300

1.8k

3.9k

300

*ADJUST FOR

BEST SQUARE WAVE

AT OUTPUT

FULL POWER

BANDWIDTH 8MHz

200

Ω*

200

Ω*

22

33

2N3866

2N5160

2N5160

2N3904

2N4440

2N3866

+15V

2N4440

OUTPUT

2N3904

2N3906

1N914

1N914

6

3

15pF

10k

1k

2

–15V

LT1001

0.01

µF

22

µF TANTALUM

22

µF TANTALUM

0.1

µF

.1

µF

–15V

200pf

.001

µF

0.01

µF

200pF

2N5486

15-60pF

TUSONIX # 519-3188

1k

DC Stabilized

1000v/

µsec Op Amp