Datasheet

Data Sheet AD736
Rev. I | Page 15 of 20
ADDITIONAL APPLICATION CONCEPTS
Figure 25 through Figure 28 show four application concepts.
Figure 25 shows the high input impedance FET input connected to
a multitap attenuator network used in various types of instruments
requiring wide ranges of voltages. For a direct network connection,
the gate-charge bleeding resistor is not required. The impedance of
the FET input is high enough (10
12
Ω) so that the loading error
is negligible. Manufacturers and distributors of the matched
precision resistor networks shown in these figures can easily be
found on the Web. The voltages shown in the diagrams are the
input levels corresponding to 200 mV at each tap. Finally, the
47 kΩ, 1 W resistor and diode pair are a practical input
protection scheme for ac line connection measurements.
Figure 26 shows both inputs connected differentially. Figure 27
shows additional components used for offset correction of the
output amplifier, and Figure 28 shows connections for single-
supply operation such as is the case for handheld devices.
Further information can be found in the AN-268 Application
Note—RMS-to-DC Converters Ease Measurement Tasks—and
the RMS to DC Converter Application Guide, both of which
can be found on the Analog Devices, Inc., website.
+V
S
+V
S
C
AV
33µF
47kΩ
1W
C
C
10µF
COM
(OPTIONAL)
OUTPUT
8
7
6
5
1
2
3
4
AD736
+
rms
CORE
+
C
C
V
IN
FULL
WAVE
RECTIFIER
C
F
–V
S
–V
S
+V
S
–V
S
C
AV
BIAS
SECTION
INPUT
AMPLIFIER
8kΩ
OUTPUT
AMPLIFIER
8kΩ
C
F
10µF
1µF
1µF
(OPTIONAL)
+
OPTIONAL
AC COUPLING
CAPACITOR
VIN FOR FULL
SCALE OUTPUT
0.01µF
1kV
2V
20V
200V
9MΩ
900kΩ
90kΩ
10kΩ
V
IN
200mV
BAV199
00834-020
Figure 25. AD736 with a High Impedance Input Attenuator
+V
S
+V
S
C
AV
33µF
COM
OUTPUT
OUTPUT
8
7
6
5
1
2
3
4
AD736
+
rms
CORE
C
C
V
IN
FULL
WAVE
RECTIFIER
C
F
–V
S
–V
S
C
AV
BIAS
SECTION
INPUT
AMPLIFIER
8kΩ
OUTPUT
AMPLIFIER
8kΩ
C
F
10µF
C
C
10µF
1µF
1µF
(OPTIONAL)
+
+IN
INPUT IMPEDANCE: 10
12
Ω||10pF
–IN
AD711
+
3
2
6
00834-021
Figure 26. Differential Input Connection