AD712 Analog Devices, AD712 Datasheet - Page 18

• Manufacturer Part Number: AD712
• Description: Precision, Low Cost, High Speed, BiFET Dual Op Amp
• Manufacturer: Analog Devices

Specifications of AD712

• -3db Bandwidth: 4MHz
• Slew Rate: 20V/µs
• Vos: 300µV
• Ib: 25pA
• # Opamps Per Pkg: 2
• Input Noise (nv/rthz): 16nV/rtHz
• Vcc-vee: 9V to 36V
• Isy Per Amplifier: 2.8mA
• Packages: DIP,SOIC

AD712
9-POLE CHEBYCHEV FILTER
Figure 50 and Figure 51 show the AD712 and its dual 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
farad-seconds. Each FDNR active network provides a two-pole
response for eight poles. The ninth pole consists of a 0.001 μF
capacitor and a 124 kΩ resistor at Pin 3 of Amplifier A2. Figure 51
depicts the circuits for each FDNR with the proper 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.
R: 24.9kΩ FOR 4.9395E
29.4kΩ FOR 5.9276E
V
IN
AD712
Figure 51. FDNR for 9-Pole Chebychev Filter
1/2
–
+
+
AD711
–
–15
–15
A1
+15V
–15V
0.1µF
0.1µF
+
1.0kΩ
R
4.99kΩ
0.001µF
0.001µF
0.001µF
100kΩ
−15
4.9395E
+
–
AD712
and 5.9276 × 10
2800Ω
1/2
+15V
–15V
–15
A
*
0.1µF
0.1µF
+
5.9276E
*
6190Ω
SEE TEXT
Figure 50. 9-Pole Chebychev Filter
–15
B
*
–15
Rev. H | Page 18 of 20
+
5.9276E
6490Ω
–15
C
*
+
4.9395E
6190Ω
–15
Figure 52. High Frequency Response for 9-Pole Chebychev Filter
D
*
REF 5.0dBm
10dB/DIV
START.0Hz
RBW 300Hz
+
0.001µF
2800Ω
124kΩ
RANGE –5.0dBm
VBW 30Hz
+
–
AD711
A2
+15V
–15V
0.1µF
0.1µF
MARKER 96 800.0Hz
STOP 200 000.0Hz
ST 69.6 SEC
4.99kΩ
4.99kΩ
V
–90dBm
OUT