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 (1012 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.

+VS

+VS

CAV

33µF

47kΩ

1W

CC

10µF

COM

(OPTIONAL)

OUTPUT

8

7

6

5

1

2

3

4

AD736

+

rms

CORE

+

CC

VIN

FULL

WAVE

RECTIFIER

CF

–VS

–VS

+VS

–VS

CAV

BIAS

SECTION

INPUT

AMPLIFIER

8kΩ

OUTPUT

AMPLIFIER

8kΩ

CF

10µF

1µF

1µF

(OPTIONAL)

+

OPTIONAL

AC COUPLING

CAPACITOR

VIN FOR FULL

SCALE OUTPUT

0.01µF

1kV

2V

20V

200V

9MΩ

900kΩ

90kΩ

10kΩ

VIN

200mV

BAV199

Figure 25. AD736 with a High Impedance Input Attenuator

+VS

+VS

CAV

33µF

COM

OUTPUT

OUTPUT

8

7

6

5

1

2

3

4

AD736

+

rms

CORE

CC

VIN

FULL

WAVE

RECTIFIER

CF

–VS

–VS

CAV

BIAS

SECTION

INPUT

AMPLIFIER

8kΩ

OUTPUT

AMPLIFIER

8kΩ

CF

10µF

CC

10µF

1µF

1µF

(OPTIONAL)

+

+IN

INPUT IMPEDANCE: 1012

Ω||10pF

–IN

AD711

+

3

2

6

Figure 26. Differential Input Connection