
LTC2754
20
2754f
APPLICATIONS INFORMATION
Op Amp Selection
Because of the extremely high accuracy of the 16-bit
LTC2754-16, careful thought should be given to op amp
selection in order to achieve the exceptional performance
of which the part is capable. Fortunately, the sensitivity of
INL and DNL to op amp offset has been greatly reduced
compared to previous generations of multiplying DACs.
Tables 4 and 5 contain equations for evaluating the effects
of op amp parameters on the LTC2754’s accuracy when
programmed in a unipolar or bipolar output range. These
are the changes the op amp can cause to the INL, DNL,
unipolar offset, unipolar gain error, bipolar zero and bipolar
gain error. Tables 4 and 5 can also be used to determine
the effects of op amp parameters on the LTC2754-12.
However, the results obtained from Tables 4 and 5 are
in 16-bit LSBs. Divide these results by 16 to obtain the
correct LSB sizing.
Table 6 contains a partial list of LTC precision op amps
recommended for use with the LTC2754. The easy-to-use
design equations simplify the selection of op amps to meet
Table 4. Coefcients for the Equations in Table 5
OUTPUT RANGE
A1
A2
A3
A4
A5
5V
1.1
2
1
10V
2.2
3
0.5
1.5
±5V
2
1
1.5
±10V
4
0.83
1
2.5
±2.5V
1
1.4
1
–2.5V to 7.5V
1.9
3
0.7
0.5
1.5
A3 VOS1 19.8
IB1 0.13
0
A4 VOS2 13.1
A4 IB2 0.13
A4
()
5V
VREF
()
5V
VREF
()
16.5k
AVOL1
OP AMP
VOS1 (mV)
IB1 (nA)
AVOL1 (V/V)
VOS2 (mV)
IB2 (mV)
AVOL2 (V/V)
VOS1 3.2
IB1 0.0003
A1
0
INL (LSB)
()
5V
VREF
()
5V
VREF
()
1.5k
AVOL1
()
66k
AVOL2
()
131k
AVOL1
()
131k
AVOL1
()
131k
AVOL2
()
131k
AVOL2
VOS1 0.82
IB1 0.00008
A2
0
DNL (LSB)
()
5V
VREF
()
5V
VREF
A3 VOS1 13.2
IB1 0.13
0
UNIPOLAR
OFFSET (LSB)
()
5V
VREF
()
5V
VREF
()
5V
VREF
VOS1 13.2
IB1 0.0018
A5
VOS2 26.2
IB2 0.26
BIPOLAR GAIN
ERROR (LSB)
()
5V
VREF
()
5V
VREF
()
5V
VREF
()
5V
VREF
BIPOLAR ZERO
ERROR (LSB)
UNIPOLAR GAIN
ERROR (LSB)
()
5V
VREF
()
5V
VREF
()
5V
VREF
()
5V
VREF
()
5V
VREF
VOS1 13.2
IB1 0.0018
A5
VOS2 26.2
IB2 0.26
Table 5. Easy-to-Use Equations Determine Op Amp Effects on DAC Accuracy in All Output Ranges (Circuit of Page 1). Subscript 1
Refers to Output Amp, Subscript 2 Refers to Reference Inverting Amp.
Table 6. Partial List of LTC Precision Ampliers Recommended for Use with the LTC2754 with Relevant Specications
AMPLIFIER
AMPLIFIER SPECIFICATIONS
VOS
μV
IB
nA
AVOL
V/mV
VOLTAGE
NOISE
nV/√Hz
CURRENT
NOISE
pA/√Hz
SLEW
RATE
V/μs
GAIN BANDWIDTH
PRODUCT
MHz
tSETTLING
with LTC2755
μs
POWER
DISSIPATION
mW
LT1001
25
2
800
10
0.12
0.25
0.8
120
46
LT1097
50
0.35
1000
14
0.008
0.2
0.7
120
11
LT1112 (Dual)
60
0.25
1500
14
0.008
0.16
0.75
115
10.5/Op Amp
LT1124 (Dual)
70
20
4000
2.7
0.3
4.5
12.5
19
69/Op Amp
LT1468
75
10
5000
5
0.6
22
90
2
117
LT1469 (Dual)
125
10
2000
5
0.6
22
90
2
123/Op Amp