OPA2652
www.ti.com
SBOS125A–JUNE 2000–REVISED MAY 2006
Differential ADC Driver
0
-5
The circuit on the front page shows an OPA2652
driving the ADS807 analog-to-digital converter (ADC)
differentially, at a gain of +2V/V. The outputs are
AC-coupled to the converter to adjust for the
difference in supply voltages. The 133Ω resistors at
the noninverting inputs minimize DC offset errors.
The differential topology minimizes even-order
distortion products, such as second-harmonic
distortion.
-10
-15
-20
-25
-30
-35
-40
Bandpass Filter
10k
100k
1M
10M
100M
Figure 31 shows a single OPA2652 implementing a
sixth-order bandpass filter. This filter cascades two
second-order Sallen-Key sections with transmission
zeros, and a double real pole section. It has 0.3dB of
ripple, –3dB frequencies of 450kHz and 11MHz, and
–23dB frequencies of 315kHz and 16MHz. The
20.0Ω resistor isolates the first OPA2652 output from
capacitive loading. This configuration improves
stability with minimal impact on the filter response.
Figure 30 shows the nominal response simulated by
SPICE.
Frequency (Hz)
Figure 30. Nominal Filter Response
2.2nF
1% Resistors
5% Capacitors
+5V
140W
2.10kW
1/2
OPA2652
VIN
1.30kW
1.0nF
1.0nF
-5V
24.9W
143W
180pF
+5V
225W
158W
2.7nF
200W
1/2
OPA2652
VOUT
18pF
12pF
150pF
20.0W
100W
100pF
-5V
24.9W
107W
Figure 31. Bandpass Filter
11
Submit Documentation Feedback
BB [ BURR-BROWN CORPORATION ]
