Datasheet

f =
-3dB
1
2 R Cp
F F
Gain(dB)
Frequency(MHz)
0.1 1 10
20
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
DifferentialGain(dB)
Frequency(MHz)
9
6
3
0
-3
-6
-9
-12
0.1 101
500100
C =8.6pF
F
OPA2690
www.ti.com SBOS238G –JUNE 2002–REVISED MARCH 2010
The frequency response for a 10MHz Butterworth Single-Supply Differential ADC Driver), the
filter is shown in Figure 45. One advantage for using 2nd-harmonic reacts as expected and drops to a
this type of filter is the independent setting of w
o
and −95dBc at 1MHz and −87dBc at 5MHz—a significant
Q. Q can be easily adjusted by changing the R
3A, B
improvement in going to differential from
resistors without affecting w
o
. single-ended.
The circuit shown on the front page has a 195MHz,
−3dB bandwidth that can be easily bandlimited by
using a capacitor in parallel with the feedback
resistors. Refer to Figure 46 for more details. The
−3dB frequency is given by Equation 6.
(6)
Figure 45. Multiple Feedback Filter Frequency
Response
SINGLE-SUPPLY DIFFERENTIAL ADC
DRIVER
The circuit shown on the front page is ideal for driving
high-frequency ADCs. As shown in the plot on the
front page (Harmonic Distortion vs Frequency for the
Figure 46. Single-Supply Differential ADC Driver
For example, C
F
= 8.6pF in parallel with R
F
= 402Ω
will control the –3dB frequency to 18MHz.
Copyright © 2002–2010, Texas Instruments Incorporated 19
Product Folder Link(s): OPA2690