Ultralow Distortion IF Dual VGA

AD8376

Rev. A

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FEATURES

Dual independent digitally controlled VGAs

Bandwidth of 700 MHz (−3 dB)

Gain range: −4 dB to +20 dB

Step size: 1 dB ± 0.2 dB

Differential input and output

Noise figure: 8.7 dB @ maximum gain

Output IP3 of ~50 dBm at 200 MHz

Output P1dB of 20 dBm at 200 MHz

Dual parallel 5-bit control interface

Provides constant SFDR vs. gain

Power-down control

Single 5 V supply operation

32-lead, 5 mm x 5 mm LFCSP

APPLICATIONS

Differential ADC drivers

Main and diversity IF sampling receivers

Wideband multichannel receivers

Instrumentation

FUNCTIONAL BLOCK DIAGRAM

POST-AMP

α

CHANNEL A

GAIN

DECODER

CHANNEL B

GAIN

DECODER

A0

A1

A2

A3

A4

B0

B1

B2

B3

B4

GNDA

VCCA

GNDB

VCCB

AD8376

IPA+

IPA–

VCMA

VCMB

OPA+

OPA+

ENBB

OPA–

OPA–

ENBA

POST-AMP

α

IPB+

IPB–

OPB+

OPB+

OPB–

OPB–

Figure 1.

GENERAL DESCRIPTION

The AD8376 is a dual channel, digitally controlled, variable gain

wide bandwidth amplifier that provides precise gain control,

high IP3, and low noise figure. The excellent distortion perform-

ance and high signal bandwidth make the AD8376 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 AD8376

achieves 50 dBm output IP3 at 200 MHz.

The AD8376 provides a broad 24 dB gain range with 1 dB

resolution. The gain of each channel is adjusted through

dedicated 5-pin control interfaces 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.

Each channel of the AD8376 can be individually powered on by

applying the appropriate logic level to the ENBA and ENBB

power enable pins. The quiescent current of the AD8376 is

typically 130 mA per channel. When powered down, the

AD8376 consumes less than 5 mA and offers excellent input-to-

output isolation, lower than −50 dB at 200 MHz.

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

the AD8376 is supplied in a compact, thermally enhanced,

5 mm × 5mm 32-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