Fixed pH measuring circuit .

[Minh Thanh]

Can you give me your opinion about this ? Whether I can take a buffer circuit to the second opamp's non-inverting input ? Thank.

 

[ericgibbs]

hi,
R1 and C1 form a filter/smoothing circuit for the PH signal.
Also if you connected the buffer output to the -inp of the 2nd stage, Vout would be inverted.

Why do you want to change the circuit.?

E

 

[Minh Thanh]

hi,
R1 and C1 form a filter/smoothing circuit for the PH signal.
Also if you connected the buffer output to the -inp of the 2nd stage, Vout would be inverted.

Why do you want to change the circuit.?

E

What happen if I detach out R1 and C1 the circuit and connecting buffer output to -inp of 2nd stage .?

 

[ericgibbs]

What happen if I detach out R1 and C1 the circuit and connecting buffer output to -inp of 2nd stage .?

hi,
If you connect the output of the buffer directly to the -inp of the 2nd stage, the amplifier will work correctly.
Why do you want to change the circuit.?
E

EDIT:
Look at these two simulations, original and modified.
Corrected the OPA supply voltages.

 

[Minh Thanh]

I mean is to connect the non- inverting input of 2nd stage not inverting input. Reason that I want to change is because I want to own a new circuit for myself . The circuit that I shown which is original circuit on a workshop web. However, If Vout will be inverted , Can I use absolute circuit to make Vout become positive ?