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In DDC112 Analog to Digital converter, its mentioned that its suitable for Low-level current output devices, such as photosensors, and can be directly connected to its inputs.

But to increase analog signal strenght it has inbuilt op amp, but how to adjust gain of this in built op-amp. ( In datasheet its mentioned that it has programmable full scale range.

Link for datasheet: http://www.ti.com/lit/ds/symlink/ddc112.pdf

Circuit diagram

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  • \$\begingroup\$ You use the "range" pins \$\endgroup\$ – Andy aka Nov 22 '14 at 10:25
  • \$\begingroup\$ Can you please explain how to increase gain like other case we use opamp but here Only resistors connected to Range pin and its connected to micro-controller. \$\endgroup\$ – Techknowlogic Nov 22 '14 at 10:31
  • \$\begingroup\$ Read the datasheet from page 9. What don't you understand? \$\endgroup\$ – Majenko Nov 22 '14 at 10:42
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With this AD converter you don't change the gain, instead you change the speed of the integrator by changing the capacity of the integrator. With a greater capacity you must provide a higher input current to get the same reading.

Some capacitors are provided on chip and you can select them with the range pins. When necessary you can provide an external capacitor for each integrator.

Given these informations one can conclude that the lowest range with the highest sensitivity is given by the chip and it's design. If that is not enough for your application you must either provide an input amplifier or use another, better suited, chip.

Please read again pages 9 and 10.

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