AD8432 Analog Devices, AD8432 Datasheet - Page 27

• Manufacturer Part Number: AD8432
• Description: Dual-Channel Ultralow Noise Amplifier with Selectable Gain and Input Impedance
• Manufacturer: Analog Devices

Specifications of AD8432

• Vcc-vee: 4.5V to 5.5V
• Isy Per Amplifier: 12mA
• Packages: CSP
• -3db Bandwidth: 200MHz
• Slew Rate: 170V/µs
• Vos: 1mV
• Ib: n/a
• # Opamps Per Pkg: 2
• Input Noise (nv/rthz): 0.8nV/rtHz

POWER SUPPLY
The AD8432 should be powered by a single 5 V supply connected
to the VPOS terminal. Separate supplies can be used for VPS1,
VPS2, and ENB, or they can all be tied to VPOS by shorting
the W3 and W4 headers and the S1 switch. Ferrite beads and
decoupling capacitors are installed for isolation, protection, and
power supply noise reduction.
INPUT TERMINATION
Active input impedance matching can be realized by installing
a feedback resistor (R
the gain and source impedance, as described in the Theory of
Operation section. C
between the input and output when using active termination;
a 0.1 µF capacitor value is recommended. The R
presents a load to OPL, and an equivalent load at OPH can be
used to balance the differential output.
Input clamping diodes (IND1 and IND2) can be connected to the
inputs by shorting the connection on the W1 and W2 headers.
The diodes provide overvoltage protection to the input and
enable faster overdrive recovery times, especially at the lowest
gain (12.04 dB).
FB
FB
), the value of which is determined by
provides the necessary ac coupling
FB
and C
FB
network
Rev. B | Page 27 of 28
OUTPUT
The AD8432 evaluation board provides the space to configure
the output loading conditions required by the user, by populating
the given footprints (for example, RL1, RL2, C7, and C8). SMA
connectors are available at the outputs, and space for a transformer
is also available for differential-to-single-ended conversion.
The 4-pin headers, PRB3 and PRB4, are placed close to the AD8432,
and they provide a way for monitoring the differential output or
the single-ended output using a high impedance differential probe.
The two inner pins of the headers are connected to OPL/OPH,
and the two outer pins of the headers are connected to ground.
There are several footprints provided to install ac coupling
capacitors at the outputs (C7 to C14). The AD8432 outputs are
biased internally at 2.5 V. To maintain the dc bias level, use coupling
capacitors between the outputs and the load.
AD8432