AD623AR-REEL Analog Devices Inc, AD623AR-REEL Datasheet - Page 15

• Manufacturer Part Number: AD623AR-REEL
• Description: IC,Instrumentation Amplifier,SINGLE,SOP,8PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD623AR-REEL

• Rohs Status: RoHS non-compliant
• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 0.3 V/µs
• -3db Bandwidth: 800kHz
• Current - Input Bias: 17nA
• Voltage - Input Offset: 25µV
• Current - Supply: 375µA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 12 V, ± 2.5 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Current - Output / Channel: -
• Gain Bandwidth Product: -

THEORY OF OPERATION
The AD623 is an instrumentation amplifier based on a modified
classic 3-op-amp approach, to assure single or dual supply
operation even at common-mode voltages at the negative
supply rail. Low voltage offsets, input and output, as well as
absolute gain accuracy, and one external resistor to set the
gain, make the AD623 one of the most versatile instrumentation
amplifiers in its class.
The input signal is applied to PNP transistors acting as voltage
buffers and providing a common-mode signal to the input
amplifiers (see Figure 41). An absolute value 50 kΩ resistor in
each amplifier feedback assures gain programmability.
The differential output is
The differential voltage is then converted to a single-ended
voltage using the output amplifier, which also rejects any
common-mode signal at the output of the input amplifiers.
Because the amplifiers can swing to either supply rail, as well as
have their common-mode range extended to below the negative
supply rail, the range over which the AD623 can operate is further
enhanced (see Figure 20 and Figure 21).
V
O
=
⎛
⎜
⎜
⎝
1
+
100
R
G
kΩ
⎞
⎟
⎟
⎠
V
C
Rev. D | Page 15 of 24
The output voltage at Pin 6 is measured with respect to the
potential at Pin 5. The impedance of the reference pin is 100 kΩ;
therefore, in applications requiring V/I conversion, a small
resistor between Pin 5 and Pin 6 is all that is needed.
Note that the bandwidth of the in-amp decreases as gain is
increased. This occurs because the internal op-amps are the
standard voltage feedback design. At unity gain, the output
amplifier limits the bandwidth.
NONINVERTING
INVERTING
GAIN
1
8
2
3
NEGATIVE SUPPLY
POSITIVE SUPPLY
Figure 41. Simplified Schematic
7
4
7
4
50kΩ
50kΩ
50kΩ
50kΩ
50kΩ
50kΩ
OTUPUT
REF
AD623
6
5