AD744S 查看數據表（PDF） - Analog Devices

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AD744S

Precision, 500 ns Settling BiFET Op Amp

Analog Devices 

AD744

Table II. Recommended Values of CCOMP vs. Various Load Conditions for the Circuits of

Figures 31 and 32.

Max

Slew

–3 dB

R1

R2

Gain

Gain

CLOAD CCOMP CLEAD Rate Bandwidth

(⍀)

(⍀)

Follower Inverter (pF)

(pF) (pF) (V/␮s) (MHz)

4.99 k 4.99 k

2

4.99 k 4.99 k

2

4.99 k 4.99 k

2

4.99 k 4.99 k

2

499 Ω 4.99 k

11

499 Ω 4.99 k

11

499 Ω 4.99 k

11

1

50

0

7

75

2.51

1

150

5

7

37

2.31

1

1000

20

–

14

1.2

1

>2000 25

–

12.52

1.0

10

270

0

–

75

1.2

10

390

2

–

50

0.85

10

1000

5

–

372

0.60

NOTES

1Bandwidth with CLEAD adjusted for minimum settling time.

2Into large capacitive loads the AD744’s 25 mA output current limit sets the slew rate of the amplifier, in V/ µs, equal to 0.025

amps divided by the value of CLOAD in µF. Slew rate is specified into rated max CLOAD except for cases marked 2, which are

specified with a 50 pF. load.

R1*

VIN

CLEAD*

+VS

R2*

1␮F

0.1␮F

AD744

VOUT

*SEE TABLE II –VS

OPTIONAL

CCOMP

1␮F

0.1␮F

Figure 32. AD744 Connected as an Inverting Amplifier

Operating at Gains of 1 or Greater

Using Decompensation to Extend the Gain Bandwidth

Product

When the AD744 is used in applications where the closed-loop

gain is greater than 10, gain bandwidth product may be enhanced

by connecting a small capacitor between Pins 1 and 5 (Figure

33). At low frequencies, this capacitor cancels the effects of the

chip’s internal compensation capacitor, CCOMP, effectively dec-

ompensating the amplifier.

Due to manufacturing variations in the value of the internal

CCOMP, it is recommended that the amplifier’s response be

optimized for the desired gain by using a 2 to 10 pF trimmer

capacitor rather than using a fixed value.

R1*

R2*

+VS

1␮F

0.1␮F

\ VIN

AD744

VOUT

NOT CONNECTED

2 – 10pF

1␮F

–VS

*SEE TABLE III

0.1␮F

Figure 33. Using the Decompensation Connection to

Extend Gain Bandwidth

Table III. Performance Summary for the Circuit of Figure 33

R1 R2 Gain

Gain

–3 dB

Gain/BW

(⍀) (⍀) Follower Inverter Bandwidth Product

1 k 10 k 11

100 10 k 101

100 100 k 1001

10

100

1000

2.5 MHz

760 kHz

225 kHz

25 MHz

76 MHz

225 MHz

REV. C

–9–

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