AD8390A 查看數據表（PDF） - Analog Devices

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AD8390A

Low Power, High Output Current Differential Amplifier

Analog Devices 

Data Sheet

THEORY OF OPERATION

VCC

INP

AD8390A

A

VCC

56kΩ

56kΩ

C

56kΩ

VEE

56kΩ

B

INN

OUTN

VCOM

OUTP

VEE

Figure 15. Functional Block Diagram

The AD8390A is a true differential amplifier with common-

mode feedback. The AD8390A is functionally equivalent to three

amplifiers, as shown in Figure 15. Amplifier A and Amplifier B

form a standard dual amplifier in an inverting configuration.

Amplifier C maintains the common-mode voltage VCOM at

the output.

With VCOM left unconnected, the outputs are internally biased

to midsupply. VCOM can be driven externally to set the dc

output common-mode voltage.

AD8390A

+

RG INP

VIN, DM

–

VCOM

RG

INN

RF

OUTN

–

OUTP

RL, DM VOUT, DM

+

RF

Figure 16. Basic Application Circuit

The high open-loop gain of the AD8390A and the negative

feedback minimize the differential and common-mode error

voltages.

With the differential and common-mode error voltages assumed

to be 0, the differential-mode gain and input impedance of the

basic application circuit shown in Figure 16 are as follows:

VOUT ,DM  R F

VIN ,DM

RG

RIN ,DM  2  RG

Rev. B | Page 9 of 12

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