AD8638ARZ Analog Devices Inc, AD8638ARZ Datasheet - Page 16

• Manufacturer Part Number: AD8638ARZ
• Description: IC OPAMP CHOPPER R-R 37MA 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD8638ARZ

• Slew Rate: 2 V/µs
• Amplifier Type: Chopper (Zero-Drift)
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Gain Bandwidth Product: 1.5MHz
• Current - Input Bias: 1pA
• Voltage - Input Offset: 3µV
• Current - Supply: 1.25mA
• Current - Output / Channel: 37mA
• Voltage - Supply, Single/dual (±): 5 V ~ 16 V, ±2.5 V ~ 8 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Op Amp Type: Low Offset Voltage
• No. Of Amplifiers: 1
• Bandwidth: 1.5MHz
• Supply Voltage Range: 5V To 16V
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD8638
OUTPUT AMPLIFIER FOR HIGH PRECISION DACS
The AD8638 can be used as an output amplifier for a 16-bit
high precision DAC in a unipolar configuration. In this case,
the selected op amp needs to have very low offset voltage (the
DAC LSB is 38 μV when operating with a 2.5 V reference) to
eliminate the need for output offset trims. Input bias current
(typically a few tens of picoamperes) must also be very low
because it generates an additional offset error when multiplied
by the DAC output impedance (approximately 6 kΩ).
Rail-to-rail output provides full-scale output with very little
error. Output impedance of the DAC is constant and code-
independent, but the high input impedance of the AD8638
minimizes gain errors. The wide bandwidth of the amplifier
also serves well in this case. The amplifier, with a settling time
of 4 μs, adds another time constant to the system, increasing the
settling time of the output. For example, see Figure 50. The
Rev. A | Page 16 of 20
settling time of the AD5541 is 1 μs. The combined settling time
is approximately 4.1 μs, as can be derived from the following
equation:
INTERFACE
SERIAL
*AD5542 ONLY
t
S
(
TOTAL
0.1µF
CS
DIN
SCLK
LDAC*
Figure 50. AD8638 Used as an Output Amplifier
V
5V
DD
)
=
DGND
AD5541/AD5542
REF(REF*)
(
t
S
2.5V
DAC
0.1µF
)
2
10µF
AGND
+
REFS*
(
t
S
AD
8638
OUT
)
2
AD8638
UNIPOLAR
OUTPUT