Tool/software:
Hi,
I would like to use this circuit for a ±10V input range while connecting -AIN to the ground.
I was wondering why a +1.5V offset is used on the positive input, and how the gain can be calculated.
For a +10V input, what would the output be?
For a -10V input, what would the output be?
Thank you,
Hi Gholam,
For a +10V input, what would the output be?
For a -10V input, what would the output be?
Here is the simulated results and it seems to be linear and acceptable.
Please make sure that you need to consider the Vout output voltage swing and do not get to close near the GND.
Please make that the Vref node has to be low output impedance and it is capable to source and sink current for proper operation. Below is an example, but most op amp should work for supply the Vref voltage.
If you have other questions, please let us know.
Best,
Raymond
Hi Gholam,
Would you please elaborate on the calculation of Vdiff? I can't understand how is -8.64 when the input is -10.
This is interesting properties of difference amplifier, where Vout = Gain*(Vin_p - Vin_n), see the simulation below.
LM7301 DA 12052024 option3.TSC
In similar application, we have INA148, INA149 and others that use this feature to interface with higher common mode voltage than an op amp's supply voltage. The example below is from INA148 in Figure 3.
https://www.ti.com/lit/ds/symlink/ina148.pdf?ts=1733462659753
If you have other questions, please let us know.
Best,
Raymond
