OPA2388: Op-Amp offset voltage

Hi Hans,

What ranges of lower offset voltage are you looking for? Based on OPA2388 and OPA2336, you'd like

1. 5Vdc single supply

2. Dual package

3. MicroAmplifier Series

4. Rail to Rail output swing

If you are able to provide us with additional performance specification, we maybe able to recommend other op amps that will meet the lower offset voltage requirements.  

As an example, OPA2336 has rated input offset voltage below. In order to duplicate the datasheet sheet Vos figures, you have to test the sample under the same specified conditions. Different common mode and supply voltages can all affect the Vos values. 

Based on the the reported value of 110uV in OPA2336 (assuming is E, P, U package), the Vos figure is within the specified datasheet (assuming the same test setup as we used in the qualification). Vos of +/-60uV is a typical value, +/-125uV is the maximum Vos figure for the package under the specified test conditions. 

If you have other questions, please let us know.

Best,

Raymond

Hi Raymond,

thank you. We are actually looking to improve our design which currently uses the OPA2336. We selected the OPA2388 based on the specs and found it was worst in our circuit.

Hi Hans,

Could you send us the schematic? It can be hand sketched, if you do not draw in a schematic tool. Please specify the op amp operating parameters and performance requirements. 

Input is 0 to +50mV and operating input frequency?

Gain of around 11

Single supply 5VDC

Expected BW

Load requirements (resistive or complex load)

Transient performance, stability analysis, etc.. 

Best,

Raymond

Hi Raymond,

schematic and BOM of how this board is built have been attached.

This is a low pass application, generally DC signals only

BW can be 1MHz or higher

Load is 10K or higher

Transient and stability have not been defined yet but the best performing amplifier is desired.

Thank you,

Hans

A81-SC-SPMC012 REV A.pdf91-SC-WA REV D.pdf

Hi Hans,

I am proposing this circuit per your requirements. 

Here are some performance of the circuit:

1. The cutoff frequency is at approx. 3.4kHz (The BW of the op amp is 100kHz). Since the application's input is generally operated in DC, this is more than adequate. 

2. With 0V at input, the Vout is simulated at 2.23mV (with Gain = 11). If this is too high,  you may consider to use lower Vos precision op amp. 

Enclosed is the Tina simulation. 

/cfs-file/__key/communityserver-discussions-components-files/14/OPA336-Vos-12022020.TSC

If you have other questions, please let us know.

Best,

Raymond

Thank you Raymond,

we need a VOS of 0.35uV or lower. Can you recommend a different amplifier for me?

Best Regards,

Hans

Hi Hans,

I just want to clarify about your design requirements. 

With 0V at the input of the above circuit (with Gain=11), the application is required to have  approx. <0.35uV*11 = 3.85uV in offset at the output.

Best,

Raymond  

Hi Raymond,

yes this would work fine for us.

Thank you,

Hans

Hi Hans,

We have two ultra low Vos op amp that may or may not meet your design requirements. I do not see anything lower than +/-1uV in Vos specification. The published Vos is rated a specific power supply voltages, Vcm, temperature etc.. Your application is required a low offset voltage at Gain of 11 in entire operating range. 

Alternatively, you may consider to compensate the offset voltage at Vin = 0V. I can send something based on OPA336, if you are interested. Please let us know. 

Best,

Raymond