Electronic – Setting LMC6001 offset voltage


I have got two LMC6001 samples.
I will use them for pH sensor interfacing.
With one LMC6001, I can cope with high input impedance errors.
But I want to set offset voltage near by to 2 V.
Can I make offset circuit with other LMC6001?

Best Answer

You don't need the second opamp. These are typical circuits for offset control in opamps which don't have offset null inputs, like the LMC6001:

enter image description here

You'll want the lower circuit, because there you can use the fA input current feature of the opamp. The other one has a much lower input impedance.

Without R3 and the potmeter this is just a non-inverting opamp where

\$ \mathrm{ V_{OUT} = \dfrac{R1 + R2}{R1} V_{IN}}\$

Adding the potmeter:

\$ \mathrm{ V_{OUT} = \left(\dfrac{R1 + R2}{R1} + \dfrac{R2}{R3} \right) V_{IN} - \dfrac{R2}{R3} V_{OFFSET} }\$