XRDAN30
Introduction
!"# $% & '' '
% ( $
& )$ $
$ $
'
% )$ )
-
-.
$
)$ $$* -.
• K
1 + S• P1
/01
Figure 2. Equivalent Circuit at Full Scale for
AC Analysis
% %$ + $ '
& Figures 3, 4 and 5.2& 3) $
& )
) $ ) 1
The Effect of DAC Output Capacitance
+Figure 1.) '
$ '
Figure 2. ( ,
4, Gain
(dB)
-
-.
-.
-
Amp Main
Pole
P1
,(% +4 2
/01
Figure 3. Op Amp Open Loop Characteristics
,(% +4 2
Figure 1. Typical Configuration CMOS IOUT
DAC with External Op Amp forming Voltage
Output Configuration
R IN
20 Lo g (
)
R IN + Rf
Gain
(dB)
R IN • R f x C O =
1
P2
Figure 4. Feedback Signal Path
Transfer Characteristics
XRDAN30
4, 5
Gain
(dB)
5
$
5
5
,(% +4 2
Figure 8. Op Amp Open Loop Characteristics
Figure 5. Root Locus
,(% +4 2
$ 6 + 2 )7 $
(Figure 6. and Figure 7.) 1 '
%$ +, 8& 9& ) 3
R IN
20 Lo g (
)
R IN + Rf
:
+2
5
R IN • R f x (C Z + C O)
6
6
"*
Figure 9. Feedback Signal Path
Transfer Characteristics
-
-.
-.
-
/01
5
6
5
Figure 6. Typical Zero Compensation of Co
General Pole
Figure 10. Root Locus
6
% (Figure 11. and Figure 12.)& ; $'
$ ) <
2
1 & $7 $ $
(Figures 13, 14, and 15)
2
1 " & $
$ =2
1 $ $
& $$* + 1 & 2
;2
* ) $ $& (% -
-.
-.
-
• K
1 + S• P1
/01
Figure 7. Equivalent Circuit at Full Scale for
AC Analysis
XRDAN30
6
,(% +4 2
20 Lo g (
R IN
)
R IN + Rf
-.
-.
-
5
:
+2
-
R A • R IN • R f x (C Z + C O)
6
"*
/01
Figure 14. Feedback Signal Path
Transfer Characteristics
Figure 11. Typical Zero Compensation of Co
General Pole
5
6
6
5
Figure 15. Root Locus
-
-.
-.
-
• K
1 + S• P1
1 ) % * ) $
(% -. /01 /01
6
Figure 12. Equivalent Circuit at Full Scale
for AC Analysis
-
4, -.
Gain
(dB)
$
5
5
-.
/01
-
-
4
/-
Figure 16. Typical Zero Compensation of Co
General Pole
,(% +4 2
Figure 13. Op Amp Open Loop Characteristics
=
4
XRDAN30
,%& $% $ % $
'
)% ? 4
1 ) % )
* )7 ( 1 ) '
$ )% 3
$ $
) Output Loading Effects
,%& ) '
$
(Figure 16.)
(% $
3
'
& 7 $ $ & ! $ ) % ( % & % $ 1 - '
% $ % ('
7 :< % $
- = @ ) &
1 ) )% = A B%
7 C A Practical Example
.& % 5D>9 5D@8< 1 5D>9 , 1 5D@8
@ , % E 7& &
5D>9 % ) = @ 5D@8 & 5D>9 B
5D@8C
$ $$ > > $
)$ 1 % )7 '
)% 1 - ? $ $
$
% $ .5. ( ;