Dual-Channel Ultralow Noise Amplifier with

Selectable Gain and Input Impedance

AD8432

Rev. 0

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FEATURES

Low noise

Input voltage noise: 0.85 nV/√Hz

Current noise: 2.0 pA/√Hz

Excellent ac specifications

200 MHz bandwidth (G = 12.04 dB)

295 V/μs slew rate

Selectable gain

G = 12.04 dB (×4)

G = 18.06 dB (×8)

G = 21.58 dB (×12)

G = 24.08 dB (×16)

Active input impedance matching

Integrated input clamp diodes

Single-ended input, differential output

Supply range: 4.5 V to 5.5 V

Low power: 60 mW/channel

APPLICATIONS

CW Doppler ultrasound front ends

Low noise preamplification

Predriver for I/Q demodulators and phase shifters

Wideband analog-to-digital drivers

FUNCTIONAL BLOCK DIAGRAM

BIAS

ENB

COMM

INH1

IND1

INL1

INH2

IND2

INL2

VPS1

VPS2

OPH1

OPL1

GMH1

GOH1

GOL1

GML1

OPH2

OPL2

GMH2

GOH2

GOL2

GML2

LNA1

LNA2

AD8432

Figure 1.

GENERAL DESCRIPTION

The AD8432 is a dual-channel, low power, ultralow noise

amplifier with selectable gain and active impedance matching.

Each amplifier has a single-ended input, differential output, and

integrated input clamps. By pin strapping the gain setting pins, four

accurate gains of G = 12.04 dB, 18.06 dB, 21.58 dB, and 24.08 dB

(×4, ×8, ×12, and ×16) are possible. A bandwidth of 200 MHz at

G = 12.04 dB makes this amplifier well suited for many high speed

applications.

The exceptional noise performance of the AD8432 is made

possible by the active impedance matching. Using a feedback

network, the input impedance of the amplifiers can be adjusted

to match the signal source impedance without compromising

the noise performance. Impedance matching and low noise of

the AD8432 allow designers to create wider dynamic range

systems that are able to detect even very low level signals.

The AD8432 achieves 0.85 nV/√Hz input referred voltage noise for

a gain of 12.04 dB. The AD8432’s ultralow noise, low distortion,

excellent gain accuracy, and channel-to-channel matching are ideal

for high performance ultrasound systems and for processing I/Q

demodulator signals.

The AD8432 operates on a single supply of 5 V at 24 mA. It is

available in a 4 mm × 4 mm, 24-lead LFSCP. The LFCSP features

an exposed paddle that provides a low thermal resistance path to

the PCB, which enables more efficient heat transfer and increases

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