Ultralow Distortion IF VGA

AD8375

Rev. 0

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FEATURES

Bandwidth of 630 MHz (−3 dB)

Gain range: −4 dB to +20 dB

Step size: 1 dB ± 0.2 dB

Differential input and output

Noise figure: 8 dB @ maximum gain

Output IP3 of ~50 dBm at 200 MHz

Output P1dB of 19 dBm at 200 MHz

Provides constant SFDR vs. gain

Parallel 5-bit control interface

Power-down feature

Single 5 V supply operation

24-lead, 4 mm × 4 mm LFCSP

APPLICATIONS

Differential ADC drivers

High IF sampling receivers

Wideband multichannel receivers

Instrumentation

FUNCTIONAL BLOCK DIAGRAM

A2

A3

A4

A1

A0

POST-AMP

α

REGISTERS

AND

GAIN DECODER

VPOS

COMM

AD8375

VCOM

VIN+

VIN–

PWUP

OUT+

OUT+

OUT–

OUT–

Figure 1.

GENERAL DESCRIPTION

The AD8375 is a digitally controlled, variable gain, wide

bandwidth amplifier that provides precise gain control, high

IP3, and low noise figure. The excellent distortion performance

and high signal bandwidth make the AD8375 an excellent gain

control device for a variety of receiver applications.

Using an advanced high speed SiGe process and incorporating

proprietary distortion cancellation techniques, the AD8375

achieves 50 dBm output IP3 at 200 MHz.

The AD8375 provides a broad 24 dB gain range with 1 dB

resolution. The gain is adjusted through a 5-pin control interface

and can be driven using standard TTL levels. The open-collector

outputs provide a flexible interface, allowing the overall signal

gain to be set by the loading impedance. Thus, the signal

voltage gain is directly proportional to the load.

The AD8375 is powered on by applying the appropriate logic

level to the PWUP pin. The quiescent current of the AD8375 is

typically 130 mA. When powered down, the AD8375 consumes

less than 5 mA and offers excellent input-to-output isolation.

Fabricated on an Analog Devices, Inc., high speed SiGe process,

the AD8375 is supplied in a compact, thermally enhanced,

4 mm × 4 mm, 24-lead LFCSP package and operates over the

temperature range of −40°C to +85°C.

–40

–60

–50

–70

–90

–80

–100

–110

65

55

60

50

40

45

35

30

40

60

80

100

120

140

160

180

200

FREQUENCY (MHz)

OIP3

HD2

HD3

Figure 2. Harmonic Distortion and Output IP3 vs. Frequency