AD623ARZ Analog Devices Inc, AD623ARZ Datasheet - Page 15

• Manufacturer Part Number: AD623ARZ
• Description: IC AMP INST R-R LP 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Low Powerr

Specifications of AD623ARZ

• Slew Rate: 0.3 V/µs
• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• -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)
• No. Of Amplifiers: 1
• Input Offset Voltage: 200µV
• Gain Db Min: 1dB
• Gain Db Max: 1000dB
• Bandwidth: 800kHz
• Amplifier Output: Single Ended
• Cmrr: 110dB
• Supply Voltage Range: 2.7V To
• Common Mode Rejection Ratio: 110
• Current, Input Bias: 17 nA
• Current, Input Offset: 0.25 nA
• Current, Supply: 550 μA
• Impedance, Thermal: 155 °C/W
• Package Type: SOIC-N
• Power Dissipation: 650 mW
• Temperature, Operating, Range: -40 to +85 °C
• Voltage, Gain: 1-1000 V/V
• Voltage, Input: -4.85 to +3.5 V
• Voltage, Input Offset: 25 μV
• Voltage, Noise: 35 nV/sqrt Hz (Input), 50 nV/sqrt Hz (Output)
• Voltage, Output Swing: 0.01 to 4.5 V
• Voltage, Supply: 2.7 to 12 V
• Rohs Compliant: Yes
• Number Of Channels: 1
• Number Of Elements: 1
• Power Supply Requirement: Single/Dual
• Input Resistance: 2000@5VMohm
• Input Bias Current: 0.025@5VnA
• Single Supply Voltage (typ): 3/5/9V
• Dual Supply Voltage (typ): ±3/±5V
• Power Supply Rejection Ratio: 80dB
• Rail/rail I/o Type: Rail to Rail Output
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 12V
• Dual Supply Voltage (min): ±2.5V
• Dual Supply Voltage (max): ±6V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• Gain Bandwidth Product: -
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

Amplifying Signals with Low Common-Mode Voltage
Because the common-mode input range of the AD623 extends
0.1 V below ground, it is possible to measure small differential
signals which have low, or no, common mode component. Fig-
ure 50 shows a thermocouple application where one side of the
J-type thermocouple is grounded.
Figure 50. Amplifying Bipolar Signals with Low Common-
Mode Voltage
Over a temperature range from –200 C to +200 C, the J-type
thermocouple delivers a voltage ranging from –7.890 mV to
10.777 mV. A programmed gain on the AD623 of 100 (R
1.02 k ) and a voltage on the AD623 REF pin of 2 V, results in
the AD623’s output voltage ranging from 1.110 V to 3.077 V
relative to ground.
INPUT DIFFERENTIAL AND COMMON-MODE RANGE
VS. SUPPLY AND GAIN
Figure 51 shows a simplified block diagram of the AD623. The
voltages at the outputs of the amplifiers A1 and A2 are given by
the equations
REV. C
V
NONINVERTING
CM
V
V
V
V
INVERTING
DIFF
DIFF
2
2
A2
A1
THERMOCOUPLE
2
3
= V
= V
= V
= V
CM
CM
CM
CM
NEG SUPPLY
POS SUPPLY
Figure 51. Simplified Block Diagram
J-TYPE
+ V
– V
+ 0.6 V + V
+ 0.6 V – V
7
4
4
7
GAIN
DIFF
DIFF
/2 + 0.6 V – V
/2 + 0.6 V + V
R
G
8
1
DIFF
DIFF
1.02k
× Gain/2
× Gain/2
A2
A1
50k
50k
R
R
R
F
F
G
DIFF
DIFF
× R
50k
50k
AD623
+5V
× R
0.1 F
F
F
/R
/R
REF
G
G
A3
50k
50k
V
2V
OUT
G
V
=
REF
OUT
6
5
–15–
The voltages on these internal nodes are critical in determining
whether or not the output voltage will be clipped. The voltages
V
supply (V– or Ground) to within about 100 mV of the positive
rail before clipping occurs. Based on this and from the above
equations, the maximum and minimum input common-mode
voltages are given by the equations
These equations can be rearranged to give the maximum possible
differential voltage (positive or negative) for a particular common-
mode voltage, gain, and power supply. Because the signals on A1
and A2, can clip on either rail, the maximum differential voltage
will be the lesser of the two equations.
However, the range on the differential input voltage range is also
constrained by the output swing. So the range of V
to be lower according the equation.
For a bipolar input voltage with a common-mode voltage that is
roughly half way between the rails, V
value that the above equations yield because the REF pin will be
at midsupply. Note that the available output swing is given for
different supply conditions in the Specifications section.
The equations can be rearranged to give the maximum gain for a
fixed set of input conditions. Again, the maximum gain will be
the lesser of the two equations.
Again, we must ensure that the resulting gain times the input
range is less than the available output swing. If this is not the
case, the maximum gain is given by,
Also for bipolar inputs (i.e., input range = 2 V
mum gain will be half the value yielded by the above equations
because the REF pin must be at midsupply.
The maximum gain and resulting output swing for different
input conditions is given in Table IV. Output voltages are refer-
enced to the voltage on the REF pin.
For the purposes of computation, it is necessary to break down
the input voltage into its differential and common-mode compo-
nent. So when one of the inputs is grounded or at a fixed voltage,
the common-mode voltage changes as the differential voltage
changes. Take the case of the thermocouple amplifier in Figure
50. The inverting input on the AD623 is grounded. So when the
input voltage is –10 mV, the voltage on the noninverting input is
–10 mV. For the purposes of signal swing calculations, this input
voltage should be considered to be composed of a common-mode
voltage of –5 mV (i.e., (+IN + –IN)/2) and a differential input
voltage of –10 mV (i.e., +IN – –IN).
A1
V
V
|V
|V
and V
CMMAX
CMMIN
DIFFMAX
DIFFMAX
Gain
A2
= V– – 0.590 V + V
Input Range
= V+ – 0.7 V – V
Gain
can swing from about 10 mV above the negative
Gain
| = 2 (V+ – 0.7 V – V
| = 2 (V
MAX
MAX
MAX
= Available Output Swing/Input Range
= 2 (V
CM
= 2 (V+ – 0.7 V – V
– V– +0.590 V)/Gain
Available Output Swing/Gain
CM
DIFF
DIFF
– V– +0.590 V)/V
× Gain/2
CM
× Gain/2
DIFFMAX
)/Gain
CM
will be half the
)/V
DIFF
DIFF
DIFF
AD623
), the maxi-
DIFF
may have