AD381KH データシートの表示（PDF） - Analog Devices
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AD381KH Datasheet PDF : 8 Pages
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Offset Null
The AD3811AD382 should not have to be offset nulled for most
applications because of its low initial offset voltage. If nulling is
required for very high precision applications, such as an output
amplifier for 13-bit or better digital-to-analog converters, connect
DIGITAL
a lOkn potentiometer between the offset null pins (pins I and 5
INPUTS
for the AD381 and pins 2 and 8 for the AD382). The wiper of
the potentiometer is tied to the negative supply. With the analog
input signal to the circuit grounded, adjust the potentiometer
for zero output.
AD7545
AD382 Heat Sinking
Figure 31. CMOS DAC Output Amplifier
A heat sink for convection cooling is required if operating at full
power and at ambient temperatures greater than 70°C. As shown
3pF
OBSOLETE in Figure 5 the free air power dissipation curve for the AD382
crosses the full power dissipation point (0.75W) at 70°C. The
power dissipation can be improved by using a heat sink up to
the case power dissipation curve (also referred to as the infinite
heat sink power dissipation curve). We recommend connecting
the heat sink to the AD382 case and keeping the combination
ungrounded. The case of the AD382 is not connected to any pin
and should be allowed to "float".
TYPICAL CIRCUITS
In many digital-to-analog converter applications, including auto-
matic test equipment, the load may be large enough to require a
buffer amplifier. The AD382 can supply:!: lOV into a 200.0
load. The AD381 can supply up to :!:10V into a 1kn load.
The AD381 and AD382 are also well suited for CMOS DAC
output amplifier applications due to their low initial offset
voltage.
10kl!
V,N
INPUT
GROUND
RF 10kl!
AD578
12-81T
AID
DIGITAL
OUTPUTS
lOkI!'
AGND
3pF'
'Optional Differential Input Components Used to Reject
Noise Between Input G..und and the AID Analog G..und.
Figure 32. Fast-Settling Buffer
Many high speed AID convertersrequire a widebandbuffer that
can hold a constant output voltage under dynamically-changing
load conditions that fluctuate at the bit decision rate.
Its quick recovery from load variations makes the AD382 an
excellent buffer for fast successive approximation AID
converters.
12-81T
DIGITAL
INPUT
Your
~
Figure 30. Buffer Amplifier to a 12-Bit Voltage Output
DAC
No external trims are required with 12-bit CMOS DACs. Since
the output impedance of CMOS DACs varies with input code,
the output voltage could appear nonmonotonic if the offset
voltage is greater than 1I2LSB. An LSB for a 12-bit DAC such
as the AD7545 is 2.44mV (10 volts full scale/4096). Thus the
AD381 and AD382, with only 1mV of offset maximum, assure
monotonic performance without external trims.
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