ANALOG DEVICES Ultralow Noise VGAs with Preamplifier and Programmable RIN AD8331 AD8332 User Manual - Specifications

Ultralow Noise VGAs with

Preamplifier and Programmable RIN

AD8331/AD8332

FUNCTIONAL BLOCK DIAGRAM

FEATURES

VIN1VIP1LOP1LON1 VPSV HILOVCM2VCM1

Ultralow noise preamplifier

Voltage noise = 0.74 n V/√Hz VPS1

Current noise = 2.5 p A/√Hz COM1

+19d B [(–48 to 0) + 21] d B

3 d B bandwidth: 120 MHz

INH1 POST

Low power: 125 m W/channel VGA 1

LNA 1 AMP1

Wide gain range with programmable postamp

–4.5 d B to +43.5 d B BIAS BIAS AND GAIN

(VMID) INTERPOLATOR INT

+7.5 d B to +55.5 d B

LMD2 VOL2

Low output-referred noise: 48 n V/√Hz typical POST

LNA 2 VGA 2

Active input impedance matching VOH2

Optimized for 10-/12-bit ADCs VPS2

CLAMP

Selectable output clamping level

6COM2

Single 5 V supply operation

VIN2VIP2LOP2LON2 ENB RCLMPCOMM

Available in space-saving chip scale package

Figure 1. AD8332 Shown 28-Lead TSSOP

APPLICATIONS

Ultrasound and sonar time-gain control VGAIN = 1V

High performance AGC systems IN (d

I/Q signal processing

High speed dual ADC driver 0.6V

GENERAL DESCRIPTION 0.4V

The AD8331/AD8332 are single- and dual-channel ultralow noise, linear-in-d B, variable gain amplifiers. Although optimized

for ultrasound systems, they are usable as low noise variable 0V

gain elements at frequencies up to 120 MHz.

Each channel consists of an ultralow noise preamplifier (LNA),

FREQUENCY (Hz)

an X-AMP® VGA with 48 d B of gain range, and a selectable gain

Figure 2. Frequency Response vs. Gain

postamplifier with adjustable output limiting. The LNA gain is 19 d B with a single-ended input and differential outputs capable

The VGA’s low output-referred noise is advantageous in driving

of accurate, programmable active input impedance matching by

high speed differential ADCs. The gain of the postamplifier may

selecting an external feedback resistor. Active impedance 9- -0

be pin selected to 3.5 d B or 15.5 d B to optimize gain range and

control optimizes noise performance for applications that

output noise for 12-bit or 10-bit converter applications. The

benefit from input matching. 9- B-

output may be limited to a user-selected clamping level, preventing input overload to a subsequent ADC. An external

The 48 d B gain range of the VGA makes these devices suitable

resistor adjusts the clamping level.

for a variety of applications. Excellent bandwidth uniformity is maintained across the entire range. The gain control interface

The operating temperature range is –40°C to +85°. The

provides precise linear-in-d B scaling of 50 d B/V for control

AD8331 is available in a 20-lead QSOP package, and the

voltages between 40 m V and 1 V. Factory trim ensures excellent

AD8332 in 28-lead TSSOP and 32-lead LFCSP packages. They

part-to-part and channel-to-channel gain matching. Differential

require a single 5 V supply, and the quiescent power

signal paths lead to superb second and third order distortion

consumption is 125 m W/ch. A power-down (enable) pin is

performance and low crosstalk.

provided.

Rev. C Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use.

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