AD8220-EVALZ Analog Devices Inc, AD8220-EVALZ Datasheet - Page 23

• Manufacturer Part Number: AD8220-EVALZ
• Description: BOARD EVAL FOR AD8220ARMZ
• Manufacturer: Analog Devices Inc

Specifications of AD8220-EVALZ

• Design Resources: Fully Isolated Input Module Based on AD7793, ADuM5401, and a High Performance In-Amp (CN0067)
• Channels Per Ic: 1 - Single
• Amplifier Type: Instrumentation
• Output Type: Single-Ended, Rail-to-Rail
• Slew Rate: 2 V/µs
• -3db Bandwidth: 1.5MHz
• Current - Output / Channel: 15mA
• Operating Temperature: -40°C ~ 85°C
• Current - Supply (main Ic): 750µA
• Voltage - Supply, Single/dual (±): 4.5 V ~ 36 V, ±2.25 V ~ 18 V
• Board Type: Fully Populated
• Utilized Ic / Part: AD8220
• Silicon Manufacturer: Analog Devices
• Application Sub Type: JFET Input Instrumentation Amplifier
• Kit Application Type: Amplifier
• Silicon Core Number: AD8220
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AD8220-EVAL; AD8220-EVAL

APPLICATIONS INFORMATION
AC-COUPLED INSTRUMENTATION AMPLIFIER
Measuring small signals that are in the noise or offset of the
amplifier can be a challenge. Figure 64 shows a circuit that
can improve the resolution of small ac signals. The large gain
reduces the referred input noise of the amplifier to 14 nV/√Hz.
Therefore, smaller signals can be measured because the noise
floor is lower. DC offsets that would have been gained by 100
are eliminated from the AD8220 output by the integrator
feedback network.
At low frequencies, the
0 V. Once a signal exceeds f
amplified input signal.
499Ω
0.1µF
0.1µF
R
+IN
–IN
10µF
+V
AD8220
+V
–V
S
S
S
10µF
Figure 64. AC-Coupled Circuit
–V
REF
S
OP1177
HIGH-PASS
0.1µF
0.1µF
f
HIGH-PASS
1µF
forces the AD8220 output to
C
, the AD8220 outputs the
+V
–V
=
OP1177
S
S
2πRC
1
15.8kΩ
R
V
REF
Rev. B | Page 23 of 28
DIFFERENTIAL OUTPUT
In certain applications, it is necessary to create a differential
signal. New high resolution ADCs often require a differential
input. In other cases, transmission over a long distance can
require differential processing for better immunity to
interference.
Figure 65 shows how to configure the AD8220 to output a
differential signal. An OP1177 op amp is used to create a
differential voltage. Errors from the op amp are common to
both outputs and are thus common mode. Likewise, errors from
using mismatched resistors cause a common-mode dc offset
error. Such errors are rejected in differential signal processing
by differential input ADCs or instrumentation amplifiers.
When using this circuit to drive a differential ADC, V
set using a resistor divider from the reference of the ADC to
make the output ratiometric with the ADC as shown in Figure 66.
AD8220
REF
can be