AD823ARZ-RL(2007) View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD823ARZ-RL Datasheet PDF : 20 Pages
| |||
Second-Order Low-Pass Filter
Figure 43 depicts the AD823 configured as a second-order
Butterworth low-pass filter. With the values as shown, the
corner frequency equals 200 kHz. Component selection is
shown in the following equations:
R1 = R2 = User Selected (Typical Values: 10 kΩ to 100 kΩ)
C1( farads) = 1.414
2πf cutoff × R1
C2 = 0.707
2πf cutoff × R1
C2
+5V
56pF
C3
R1
R2
0.1µF
20kΩ 20kΩ
VIN
1/2
C1
AD823
28pF
VOUT
50pF
C4
0.1µF
–5V
Figure 43. Second-Order Low-Pass Filter
A plot of the filter is shown in Figure 44; better than 50 dB of
high frequency rejection is provided.
0
–10
VDB – VOUT
–20
–30
–40
–50
–60
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 44. Frequency Response of Filter
100M
AD823
Single-Supply Half-Wave and Full-Wave Rectifiers
An AD823 configured as a unity-gain follower and operated
with a single supply can be used as a simple half-wave rectifier.
The AD823 inputs maintain picoamp level input currents even
when driven well below the minus supply. The rectifier puts
that behavior to good use, maintaining an input impedance of
over 1011 Ω for input voltages from within 1 V of the positive
supply to 20 V below the negative supply.
The full-wave and half-wave rectifier shown in Figure 45
operates as follows: when VIN is above ground, R1 is boot-
strapped through the unity-gain follower A1 and the loop of
Amplifier A2. This forces the inputs of A2 to be equal, thus no
current flows through R1 or R2, and the circuit output tracks
the input. When VIN is below ground, the output of A1 is forced
to ground. The noninverting input of Amplifier A2 sees the
ground level output of A1; therefore, A2 operates as a unity-
gain inverter. The output at Node C is then a full-wave rectified
version of the input. Node B is a buffered half-wave rectified
version of the input. Input voltage supply to ±18 V can be
rectified, depending on the voltage supply used.
R1
100kΩ
R2
100kΩ
+VS 0.01µF
A
8
6
3
1
7
5 AA22
C
VIN
2 A1
1/2
1/2
AD823
FULL-WAVE
RECTIFIED OUTPUT
4 AD823
B
HALF-WAVE
RECTIFIED OUTPUT
Figure 45. Full-Wave and Half-Wave Rectifier
2V
100
A 90
200µs
B
10
C 0%
2V
Figure 46. Single-Supply Half-Wave and Full-Wave Rectifier
Rev. B | Page 17 of 20
Share Link: 