AnsweredAssumed Answered

ADA4851 differences between single and dual

Question asked by sv1eed on Jun 25, 2013
Latest reply on Jul 4, 2013 by sv1eed

hello everyone,
i am having a hard time understanding the huge difference in behavior that i see between the single (ADA4851-1) and dual (ADA4851-2) versions of this amplifier.
my supply is +- 5V
my input is a DC to 10mhz, 0 to 1v sinewave
i am testing both versions of the chip (dual and single)

 

the input signal goes directly to the non-inv input,
the feedback res is 100k and another 100k goes from the inverting input to a variable voltage to control the output offset.
the output has no load except a 10x probe

 

the dual version, works somewhat as expected, but for the single version the output gain varies hugely for some frequency ranges.
i tried lowering the resistor values to 10k and to 1k, but then i get something that looks like a crossover distortion on the output (when i vary the offset control voltage).

 

in general, the desired output is a fixed gain of about 2 or 3, relatively stable across the DC to 10mhz input range, with wide output offset control.
the dual version seems to do ok (regarding the large resistor values), but the single version does not.

 

this is my 1st post here, so excuse me if i missed some important formality or something like that.
thank you for your time and help,
- Chris

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