AD823A Analog Devices, AD823A Datasheet - Page 15

• Manufacturer Part Number: AD823A
• Description: Dual, 16 Mhz, Rail-to-rail Fet Input Amplifier
• Manufacturer: Analog Devices

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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’s 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
10
20 volts below the negative supply.
The full- and half-wave rectifier shown in Figure 43 operates as
follows: when V
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
V
noninverting input of amplifier A2 sees the ground level output
of A1, therefore, A2 operates as a unity gain inverter. The out-
IN
11
is below ground, the output of A1 is forced to ground. The
for input voltages from 1 volt from the positive supply to
–10
–20
–30
–40
–50
–60
Figure 42. Frequency Response of Filter
0
1k
IN
is above ground, R1 is bootstrapped through
10k
FREQUENCY – Hz
100k
V
1M
DB
– V
OUT
10M
100M
–15–
put 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 volts can be rectified, depending on
the voltage supply used.
V
A
IN
Figure 43. Single Supply Half- and Full-Wave Rectifier
A
B
C
2
3
100
90
10
0%
+V
8
A1
S
4
2V
AD823
100k
2V
R1
1
1/2
0.01 F
2V
6
5
A2
100k
AD823
R2
1/2
7
200 s
HALF-WAVE
RECTIFIED OUTPUT
FULL-WAVE
RECTIFIED OUTPUT
AD823
C
B