DC to 600 MHz,

Dual-Digital Variable Gain Amplifiers

AD8366

Rev. A

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FEATURES

Matched pair of differential, digitally controlled VGAs

Gain range: 4.5 dB to 20.25 dB

0.25 dB gain step size

Operating frequency

DC to 150 MHz (2 V p-p)

3 dB bandwidth: 600 MHz

Noise figure (NF)

11.4 dB at 10 MHz at maximum gain

18 dB at 10 MHz at minimum gain

OIP3: 45 dBm at 10 MHz

HD2/HD3

Better than −90 dBc for 2 V p-p output at 10 MHz at

maximum gain

Differential input and output

Adjustable output common-mode

Optional dc output offset correction

Serial/parallel mode gain control

Power-down feature

Single 5 V supply operation

APPLICATIONS

Baseband I/Q receivers

Diversity receivers

Wideband ADC drivers

FUNCTIONAL BLOCK DIAGRAM

VPSIA

IPPA

IPMA

ENBL

ICOM

IPMB

IPPB

VPSIB

BIT0/CS

BIT1/SDAT

BIT2/SCLK

BIT3

OCOM

BIT4

BIT 5

DENA

DIGITAL GAIN

CONTROL LOGIC

Figure 1.

GENERAL DESCRIPTION

The AD8366 is a matched pair of fully differential, low noise and

low distortion, digitally programmable variable gain amplifiers

(VGAs). The gain of each amplifier can be programmed separately

or simultaneously over a range of 4.5 dB to 20.25 dB in steps of

0.25 dB. The amplifier offers flat frequency performance from dc

to 70 MHz, independent of gain code.

The AD8366 offers excellent spurious-free dynamic range, suitable

for driving high resolution analog-to-digital converters (ADCs).

The NF at maximum gain is 11.4 dB at 10 MHz and increases

~2 dB for every 4 dB decrease in gain. Over the entire gain range,

the HD3/HD2 are better than −90 dBc for 2 V p-p at the output at

10 MHz into 200 Ω. The two-tone intermodulation distortion of

−90 dBc into 200 Ω translates to an OIP3 of 45 dBm (38 dBVrms).

The differential input impedance of 200 Ω provides a well-defined

termination. The differential output has a low impedance of ~25 Ω.

be programmed via the VCMA and VCMB pins over a range

of voltages. The input common-mode voltage also defaults

compensation loop can be used to eliminate dc offsets from prior

stages in the signal chain. This loop can also be disabled if dc-

coupled operation is desired.

The digital interface allows for parallel or serial mode gain

programming. The AD8366 operates from a 4.75 V to 5.25 V

supply and consumes typically 180 mA. When disabled, the

part consumes roughly 3 mA. The AD8366 is fabricated using

Analog Devices, Inc., advanced silicon-germanium bipolar

process, and it is available in a 32-lead exposed paddle LFCSP

package. Performance is specified over the −40°C to +85°C

temperature range.