AD712
+15V
0.1µF
+15V
0.1µF
0.001µF
2800Ω
4.9395E
–15
A
6190Ω
5.9276E
–15
6490Ω
5.9276E
–15
6190Ω
4.9395E
–15
2800Ω
V
IN
+
A1
AD711
–
+
A2
0.1µF
+
B
+
C
+
D
+
AD711
–
V
OUT
0.1µF
4.99kΩ
–15V
100kΩ
*
*
*
*
0.001µF
124kΩ
–15V
00823-050
4.99kΩ
*
SEE TEXT
Figure 50. 9-Pole Chebychev Filter
9-POLE CHEBYCHEV FILTER
counterpart, the AD711, as a 9-pole Chebychev filter using
active frequency dependent negative resistors (FDNRs). With a
cutoff frequency of 50 kHz and better than 90 dB rejection, it
can be used as an antialiasing filter for a 12-bit data acquisition
system with 100 kHz throughput.
As shown in Figure 50, the filter is comprised of four FDNRs
(A, B, C, D) having values of 4.9395 × 10
−15
and 5.9276 × 10
–15
farad-seconds. Each FDNR active network provides a two-pole
response for a total of eight poles. The ninth pole consists of a
0.001 μF capacitor and a 124 kΩ resistor at Pin 3 of Amplifier A2.
selection of R. To achieve optimal performance, the 0.001 μF
capacitors must be selected for 1% or better matching and all
resistors should have 1% or better tolerance.
+
0.001µF
+15V
0.1µF
+
1/2
R
AD712
–
0.1µF
1/2
AD712
Figure 51. FDNR for 9-Pole Chebychev Filter
REF 5.0dBm
10dB/DIV
MARKER 96 800.0Hz
–90dBm
RANGE –5.0dBm
START.0Hz
RBW 300Hz
VBW 30Hz
STOP 200 000.0Hz
ST 69.6 SEC
Figure 52. High Frequency Response for 9-Pole Chebychev Filter
Rev. G | Page 18 of 20
00823-052
00823-051
R:
24.9kΩ FOR 4.9395E
–15
29.4kΩ FOR 5.9276E
–15
–
0.001µF
–15V
1.0kΩ
4.99kΩ
+
AD [ ANALOG DEVICES ]
