AD605 Просмотр технического описания (PDF) - Analog Devices

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AD605

Dual, Low Noise, Single-Supply Variable Gain Amplifier

Analog Devices 

AD605

EVALUATION BOARD

The AD605-EVALZ provides a platform for the circuit designer

to become familiar with the many operating and performance

features of the AD605 variable gain amplifier. It is a factory-

designed, surface-mount assembly fully tested and ready for

service. Figure 42 is a photograph of the AD605-EVALZ. Multiple

inputs, test points, and jumpers provide circuit configurations that

support any of the operating options of the device. Figure 43 is a

schematic of the board.

Power is required from only a single 5 V supply capable of

supplying 55 mA to 60 mA quiescent current.

Figure 42. AD605–EVALZ Evaluation Board

INPUT CONNECTIONS

The AD605 VGA accepts differential or single-ended input

signals and provides single-ended outputs. The SMA connectors

enable either configuration to be used, as well as the output and

gain control signals. Each of the I/O ports is also available at a

test-loop labeled for easy identification.

The input resistance at each of the four input SMA connectors is

50 Ω, consisting of the 175 Ω, ±40 Ω resistance of the attenuator

ladder network in parallel with the external 69.8 Ω resistors. For

single-ended operation, unused inputs can be left disconnected

or optional jumpers installed. Either VGA input is usable; for

noninverting operation, the INPx is used, and for signal inversion,

the INMx is used.

ADJUSTING GAIN, COMMON-MODE, AND

REFERENCE LEVELS

The gain of each channel is adjusted with trimmers, GN1ADJ and

GN2ADJ. Trimmer VREF ADJ adjusts the gain scaling in dB/V (or

gain slope), and VOCM ADJ adjusts the output common-mode

voltage for both channels. For dynamic gain control, JP1 and

JP4 can be removed and the signal applied at the SMA

connectors, GN1 and GN2.

OUTPUT CONNECTIONS

SMA connectors, OUT1 and OUT2, are the output connectors.

Series resistors and capacitors are included for termination and

dc blocking purposes. The output of the AD605 has a common-

mode value of one-half the supply (unless amended by a voltage

applied to the VCM pin).

Table 4 lists jumpers and their functions, and Figure 44 shows

the evaluation board in a typical test configuration.

Table 4. Table of Jumpers

Jumper Function

JP1

Connects trimmer GN1ADJ to pin VGN1. This jumper can be removed for an ac signal at VGN1.

JP2

Grounds the IN1 pin via C2.

JP3

Grounds the IN2 pin via C5.

JP4

Connects trimmer GN2ADJ to Pin VGN2. This jumper can be removed for an ac signal at VGN2.

JP5

Connects trimmer VOCMADJ to the VOCM pin. This jumper can be removed for the half supply default VOCM.

JP6

Shifts the gain of Channel 2 up or down by 14 dB.

JP7

Shifts the gain of Channel 1 up or down by 14 dB.

JP8

Connects trimmer VREFADJ to the VREF pin to change the gain slope.

Default Configuration

Installed

User supplied

User supplied

Installed

Installed

Installed

Installed

Installed

Rev. F | Page 18 of 24

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