REV. B

–10–

AD817

OFFSET NULLING

The input offset voltage of the AD817 is inherently very low.

However, if additional nulling is required, the circuit shown in

Figure 32 can be used. The null range of the AD817 in this con-

figuration is

±15 mV.

AD817 SETTLING TIME

Settling time is comprised primarily of two regions. The first is

the slew time in which the amplifier is overdriven, where the

output voltage rate of change is at its maximum. The second is

the linear time period required for the amplifier to settle to

within a specified percent of the final value.

0.10

0.20

0.15

0.05

0.05

0

0

4

6

10

8

2

0

350

400

300

250

200

150

100

50

Figure 33. Settling Time in ns 0 V to +10 V

Measuring the rapid settling time of AD817 (45 ns to 0.1% and

70 ns to 0.01%–10 V step) requires applying an input pulse with

a very fast edge and an extremely flat top. With the AD817 con-

figured in a gain of –1, a clamped false summing junction re-

sponds when the output error is within the sum of two diode

voltages (ª1 volt). The signal is then amplified 20 times by a

clamped amplifier whose output is connected directly to a sam-

pling oscilloscope. Figures 33 and 34 show the settling time of

the AD817, with a 10 volt step applied.

0.05

0.05

0

0.20

0.10

0.15

–10

–6

–4

0

–2

–8

0

350

400

300

250

200

150

100

50

Figure 34. Settling Time in ns 0 V to –10 V

AD829

100

Ω

0.47

µF

0.01

µF

+V

S

0.47

µF

0.01

µF

–V

S

SHORT, DIRECT

CONNECTION TO

TEKTRONIX TYPE 11402

OSCILLOSCOPE PREAMP

INPUT SECTION

SETTLING

OUTPUT

2

×

HP2835

ERROR AMPLIFIER

V

2

×

HP2835

1.9k

Ω

100

Ω

AD817

0.01

µF

+V

S

0.01

µF

2.2

µF

–V

S

2.2

µF

10pF

SCOPE PROBE

CAPACITANCE

TEKTRONIX P6201

FET PROBE TO

TEKTRONIX TYPE

11402

OSCILLOSCOPE

PREAMP INPUT

SECTION

500

Ω

5–18pF

DEVICE

UNDER

TEST

NOTE:

USE CIRCUIT BOARD

WITH GROUND PLANE

FALSE

SUMMING

NODE

NULL

ADJUST

1k

Ω

100

Ω

1k

Ω

50

Ω

COAX

CABLE

TTL LEVEL

SIGNAL

GENERATOR

50Hz

OUTPUT

7, 8

0 TO

±10V

POWER

SUPPLY

EI&S

DL1A05GM

MERCURY RELAY

ERROR

SIGNAL

OUTPUT

500

Ω

50

Ω

6

3

2

4

15pF

1M

Ω

7

6

3

2

4

5

13

2

1, 14

DIGITAL

GROUND

ANALOG

GROUND

7

Figure 35. Settling Time Test Circuit