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AD8132 - output offset control

Question asked by meir.mardechayev@phnx.co.il on Feb 18, 2014
Latest reply on Feb 20, 2014 by meir.mardechayev@phnx.co.il

Hello,

 

My name is Meir and I am DFAE at Phoenix technologies in Israel.

 

VAYYAR, one of my customers is interested in AD8132 for RF application. They have got a samples and evaluate the functionality.

 

They build a circuit as in Figure.56 in the datasheet: Vcc=3.3v,VSS=0.

 

They rty set the Vocm to 0.6V

At input they have 1MHz signal, 200mV-ptp, 0.5v-offset

 

At output:

  • Very large gain difference between the two output ports
  • Gains change in wide range when changing input signal offset level
  • Total differential output level is about x0.5 vs. input ( expected G=1)

 

After changing Vocm voltage to ~1.6v - performance is better.

  • When Vocm is at ~1.6v  - then output common level is 1.6v

 

When Vocm-pin is at 0.8v    - then output common level and gains are not stable

 

According to data sheet in test condition according to Table3, Output Voltage Swing is 1V from RAILS: VSS(0V) and VCC(5V).

 

Is it any limitations on  Vocm in condition when: Vcc=3.3v, VSS=0?

In this condition the Output Voltage Swing is also 1V from RAILS?

 

In case of this component can not function with Vocm=0.8, please advice if there is any other solution for this application? (maybe AD8138, OR OTHER...?)

 

Best Regards,

Meir

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