Datasheet

Detailed Description
The MAX2034 is a four-channel, ultra-low-noise pream-
plifier. Each amplifier features single-ended inputs, dif-
ferential outputs, and provides an accurate fixed gain of
19dB with a wide -3dB bandwidth of 70MHz. The high-
gain accuracy of the amplifier allows for exceptional
channel-to-channel gain matching, which is necessary
for high-performance ultrasound-imaging applications.
The device has an exceptionally low noise figure, making
it ideal for use in ultrasound front-end designs. Noise fig-
ure is typically 2.2dB for a source impedance and pro-
grammed input impedance of 200Ω.
The MAX2034 is optimized for excellent dynamic range
and linearity performance characteristics, making it ideal
for ultrasound-imaging modalities including second har-
monic 2D imaging and continuous wave Doppler. The
device achieves an HD2 of -68dBc at V
OUT
= 1V
P-P
and
f
IN_
= 5MHz, and an ultrasound-specific two-tone IMD3
performance of -55dBc at V
OUT
= 1V
P-P
and f
IN_
=
5MHz. See the Ultrasound-Specific IMD3 Specification in
the Applications Information section.
Active Impedance Matching
To provide exceptional noise-figure characteristics, the
input impedance of each amplifier uses a feedback
topology for active impedance matching. A feedback
resistor of the value (1 + (A / 2)) x R
S
is added between
the inverting output of the amplifier to the input. The
input impedance is the feedback resistor, Z
F
, divided
by 1 + (A / 2). The factor of two is due to the gain of the
amplifier, A, being defined with a differential output. For
common input impedances, the internal digitally pro-
grammed impedances can be used (see Table 1). For
other input impedances, program the impedance for
external resistor operation, and then use an externally
supplied resistor to set the input impedance according
to the above formula.
The gain and input impedance of the MAX2034 vs. fre-
quency are shown in the Typical Operating Char-
acteristics. Both gain and input impedance are well
behaved, with no peaking characteristics. This allows
the device to be used with a variety of input networks,
with no requirement for series ferrite beads or shunt
capacitors for stability control.
MAX2034
Quad-Channel, Ultra-Low-Noise Amplifier with
Digitally Programmable Input Impedance
_______________________________________________________________________________________ 7
Pin Description (continued)
PIN NAME FUNCTION
18, 19, 42
D1, D0, D2
Digitally Programmable Inputs. Programs the input impedance of each amplifier. See Table 1 on
input impedance programming information.
23 OUT4- Channel 4 LNA Analog Inverting Output
24 OUT4+ Channel 4 LNA Analog Noninverting Output
28 OUT3- Channel 3 LNA Analog Inverting Output
29 OUT3+ Channel 3 LNA Analog Noninverting Output
31 OUT2- Channel 2 LNA Analog Inverting Output
32 OUT2+ Channel 2 LNA Analog Noninverting Output
35 OUT1- Channel 1 LNA Analog Inverting Output
36 OUT1+ Channel 1 LNA Analog Noninverting Output
43 PD Power-Down. Drive PD high to put the device in sleep mode. Drive PD low for normal mode.
47 ZF1 Channel 1 Active Impedance-Matching Port. AC-couple to the source circuit with a capacitor.
48 IN1
Channel 1 LNA Analog Input. Single-ended input for channel 1 amplifier. Connect the analog input to
the source circuit through a series capacitor.
EP GND Exposed Paddle. Solder the exposed paddle to the ground plane using multiple vias.
D2 D1 D0 R
IN
(Ω)
000 50
001 100
010 200
011 1k
100
101
110
111
Defined by external resistor
Table 1. Digitally Programmable Input
Impedance