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# INA322: INA322

Part Number: INA322

Hi,

I need support for INA322.

I attached the TINA file and we have a protoype. Vd is sinewave, amplitude 500uV 0DC 1kHz.... Vcm=2.5V.

The issue is that at the output DC value is higher than 500mV.

For example if we short V+ and V- with a Vcm=2.5V the output should be Vref.... and the simulation confirms that.

On the prototype, when we short V+/V- the output is higher than Vref... for example if Vref is 200mV, at the output we have about 250mV. Resistors used are 0.1% tolerance. Gain is 500.

Can you suppor me?

Thanks.

Best Regards.

Anthony

• Hello Anthony,

Best Regards,

Chris Featherstone

• Here is TINA file

• Hello Anthony,

Keep in mind that the input offset voltage ranges from 1mV to 10mV and in a gain of 500 you can see 500 mV if the offset voltage is 1mV. If you lower the gain down to 50 does the output follow and reduce to 50 mV?

Best Regards,

Chris Featherstone

• Hi Chris,

with G=500, vref=200mV, shorting V+/V-, Vcm=1.65V and Power Supply 3.3V we see at the output about 250mV. If the input offset 2-10mV is amplified 500 at the output we should see an higher value than 250mV. f we set a lower gain the the output is closer to 200mV.

Why the simulator shows always an ideal value of 200mV at the output? Does not it consider the real parameters of the TINA model?

It is just to understand the origin of this delta-value respect to Vref. Ideally, at the output we should see Vref with V+/V- shorted.

Best Regards

Antonio

• Hello Antonio,

Given the age of when the device was created I don't believe the model is as accurate unfortunately. Our models today are very good and show typical values for offset for example. The INA322 model is not showing this.

Best Regards,

Chris Featherstone

• Hi Chris,

ok for TINA model... but on the prototype if the reason is the input offset amplified (G=500, V+/V- shorted) we should see an higher value (Vref + input offset*500)... instead we see 200mV+50mV.

Best Regards

Antonio

• Hey Antonio,

Are you seeing a consistent additional 50 mV from part to part? Theoretically you should see some variation of offset voltages gained up as shown below.

Best Regards,

Chris Featherstone