I my application, i use AD835 to get a*b, which a and b all are DC.

In AD835 datasheet, it say output offset is +-25mV, and input offset voltage is +-20mV ~ +-75mV, how can i cancel this offset?

Or how can i measure this offset.

Thanks.

I my application, i use AD835 to get a*b, which a and b all are DC.

In AD835 datasheet, it say output offset is +-25mV, and input offset voltage is +-20mV ~ +-75mV, how can i cancel this offset?

Or how can i measure this offset.

Thanks.

Hi jiangfux,

Apologies for the delay of response. Offset voltage exists inherently due to some non-idealistic property of the amplifier. If you really need to eliminate this offset, I think you can use the Z input pin to calibrate and compensate the offset voltage you are seeing. You can measure and calculate the actual input and output offset voltage of your device by doing some algebra.. You have to use three point system: Given that your circuit is the same with figure 20 of its datasheet. You can do the following.

1. Measure the output voltage for the following inputs:

a. X = 0V, Y = 0V and Z = 0V

b. X = 0.3V, Y = 0.4V and Z = 0V

c. X = 1V, Y - 1V and Z = 0V

2. Substitute the actual values on this equation to get the three equations:

3. Use algebra to get the value of the Vosix (input offset voltage at X input), Vosiy (input offset voltage at Y input) and Voso (output offset voltage)

I hope this helps!

Let me know if you have any other concern.

Best Regards,

Emman

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Hi Jianfux,

If R1 and R2 is not present on your circuit, the nominally value of U is 1.05. However, you can adjust the value of U through the use of a resistive divider between pin W (Pin 5) and Z (Pin 4). If you use R1 = 20 x R2, then effective value of U will be equal to 1.

I hope this helps!

Thanks,

Emman

Hi jiangfux,

Apologies for the delay of response. Offset voltage exists inherently due to some non-idealistic property of the amplifier. If you really need to eliminate this offset, I think you can use the Z input pin to calibrate and compensate the offset voltage you are seeing. You can measure and calculate the actual input and output offset voltage of your device by doing some algebra.. You have to use three point system: Given that your circuit is the same with figure 20 of its datasheet. You can do the following.

1. Measure the output voltage for the following inputs:

a. X = 0V, Y = 0V and Z = 0V

b. X = 0.3V, Y = 0.4V and Z = 0V

c. X = 1V, Y - 1V and Z = 0V

2. Substitute the actual values on this equation to get the three equations:

3. Use algebra to get the value of the Vosix (input offset voltage at X input), Vosiy (input offset voltage at Y input) and Voso (output offset voltage)

I hope this helps!

Let me know if you have any other concern.

Best Regards,

Emman