TLV2374: Lost gain in non-inverting stage

Sounds like a possible voltage divider or impedance mismatch. Can you share the relevant portion of the schematic?

Some further questions:
* Is the error always 50%, regardless of input voltage?
* What load is on the output of the unity gain buffer?
* What is the amplitude and frequency of the input signal you're testing?

-Paul

The circuit is very simple just a 1 meg resistor going to non-inverting input .

The op amp stage is unity gain. See picture.

I put a 5 volt DC signal into the input and there is 2.5 volts lost across the 1 meg resistor.

If that is true then the input current to op amp is 2.5uA when spec says it should be about 1pA typical.

Hi Nigel,

shouldn't it be this way?

Kai

No, the circuit is meant to be the front end of an oscilloscope and the 1 meg protects the op amp as the input can be as high as 160 volts.
I am going to add an attenuator circuit after the 1 meg to bring down the input voltage.

I applied 5 volts to input and power supply is only 3.3 volts so that's why I only got a couple of volts out. Sorry !

I checked again with an AC signal and that is about 50% down at 20KHz.
So its probably more like a bandwidth problem or input capacitance problem.