AD509KH AD [Analog Devices], AD509KH Datasheet - Page 4

• Manufacturer Part Number: AD509KH
• Description: HIGH SPEED FAST SETTING IC OP AMP
• Manufacturer: AD [Analog Devices]

,
'lumped singJe point (the V+ point). The V+ to V- O.lIlF
dominate total settling time. And for a 12-bit DAC, one least
significant bit is only 0,024% of full-scale, so low drift and
high linearity and precision are also required of tbe output
amplifier.
voltage convc:;rsion m ode.
The senling time of the combination depends on the settling
time of the DAC and the output amplifier. A good approxima-
Some IC DACs settle to final output value in 100-500 nano-
seconds. Since most IC op amps require a longer time to settle
to :1:0.1% or :1:0.01%of final value, amplifier settling time can
AD509
DYNAMIC RESPONSE OF ADS09
THE ADS09 AS AN OUTPUT AMPLIFIER FOR FAST
CURRENT -OUTPUT D-TO-A CONVERTERS
Most fast integrated circuit digital to analog converters have
current outputs. That is, the digital input code is translated
to an output current proportional to the digital code. In
many applications, that output current is converted to a volt-
age by connecting an operational amplifier in the current-to-
tion is:
The O.lIlF cetatnic power supply bypass capacitors are
considerably more important for the AD509 than for low
frequency general purpose amplifiers. Their main purpose
is to convert the distributed high frequency ground to a
capacitor equalizes the supply grounds while the O.lIlF
capacitor from V+ to signal ground should be returned to
signal common. The signal common, which is bypassed to
pin 7, is defined as that point at which the input signal
source, tltc feedback network, and tbe retUrn side of the load
are joined to the power common,
Note that the diagram shows each individual capacitor
directly connected to the appropriate terminal (pin 7 [V+).
ANALOGDEVICES fAX-ON-DEMAND HOTLINE
~:i
8'
z'"
..!
_INVERTING
~
,100
...
Figunt 5. Configuration for Unity Gain Applications
Figure 6. Open Loop Frequency and Phase Response
INVERTING
-20
Is TOTAL
120
<10
20
10
80
II
.0
INPUT
INPUT
100
=
.JCt~DAC)
..
FREQUENCY-II,
1011
'
2
CEIlAMIe OISe
+
1OOOt
O.,..F
( ts AMP) 2
1M
-
Page
TO SIGNAL
COMMON
10M
15
OUTPUT
100M
POINT
30'
-4-
AD565K/ADS09K combination settles to :to.Ol% in one
microsecond. The low input voltage drift and high open loop
gain of the ADSO9K assures 12-bit accuracy over the operating
temperature range.
with the ADS65K, high speed 12-bit IC digital-to-analog con-
Figure 8 shows the AD509K connected as an output amplifier
verter. The 10 picofarad capacitor, Cl, compensates for the
2SpF AD56S output capacitance. The voltage output of the
direct, and as physically dose to the case as possible, so that
components will be minimized.
Avoid pole-zero mismatches in any feedback networks used
with the amplifier. Minimize noise pickup,
the length of any conducting path shared by external
than wire wound types, and are available with excellent
accuracies and temperatUre coefficients.
Diodes are hot carrier types for the very fastest-settling
Capacitors in critical locations are polystyrene, teflon, or
polycarbonate to minimize dielectric absorption.
CIRCUIT. For the fastest settling times, keep leads short,
orient components to minimize stray capacitance, keep
circuit impedance levels as low as consistent with the out-
put capabilities of the amplifier and the signal source,
reduce all extemalload
minimum. Don't overlook sockets or printed circuit
board mounting as possible sources of dielectric absorption.
[n addition, it is suggested that all connections be sbort and
COMPONENTS. Resistors are preferably metal fIlm types.
because they have less capacitance and stray inductance
applications, but lN914 types are suitable for more
routine uses.
Output D-tO-AConvert",
Figure8. AD509 as an Output Amplifier for B Fast Current-
Figure7. Open Loop Frequency Response for VariousCc's
-20
.0
AD566K
100
..
capacitances to the absolute
SkU
FREQUENCY
101<
IOOIt
~
-
H.
.
1M
10M
"
100M