Buffer Amplifier's Questions

Is the ground for the opamps the same as for the IC? They must be the same for any of this to work.

How are the opamps connected? The inputs of opamps are usually very high impedance, meaning they will source or sink only tiny amounts of current. However, if you hook them up in certain feedback configurations, the feedback can source or sink current, possibly causing the problem. If this is your problem, then just using another opamp as a buffer seems like it may work.

Thanks Robert.

The grounds of the Op-Amp and the IC are the same.

I'm doing a project which does the calculation of addition and subtraction of voltages which involve Vref. For the circuit's configurations, pls refer to

After adding the buffer amplifier to the Vref, the IC's still burnt. (Note: Vref is one of the point in the IC). Any suggestions? Or any experience to share?

Have you replaced the burnt IC? When you say "burnt" - do you mean it gets hot when your external circuitry is attached - or, is it burnt-out? Have you replaced it?

Does it get hot now even without the external circuiry, or only when it is connected?

Are you sure you are only connecting outputs to inputs? Could it be output-to-output i.e. outputs fighting each other?

Have you observed the test point on an oscilloscope or multimeter? Does the voltage / signal level at the test point change when you connect the external circuitry? That would be a sure sign of a short-circuit.

Can you post a schematic of your circuitry? Can you give more details of the circuit and/or what you are trying to achieve?

Thanks.

The "burnt" i meant is the IC is damaged. I could see some "sparks" come out. After the IC is being replaced, the drive becomes okay again?

Yup... the Vref voltage that's supposed to be ~1.945V would change to ~10V or above when we connected it to the external circuit.

I attach the link to my circuit diagram and also the drive's IC TZA1047 as below:

My design will take 5 voltage signals from the IC TZA1047, which are Vref, A, B, C and D. My circuit will first perform (A - Vref), (B - Vref), (C - Vref) and (D - Vref) (Note: Let A*= (A-Vref), B* = (B-Vref) and so on.)

Then, A*, B*, C* and D* will go into a circuit which does

Vout= [(A*+D*)-(B*+C*)]/(A*+B*+C*+D*)

The addition and subtraction part will be done by INA105kp while the division part will be done by mpy634.

The following are the links of the datasheets for INA105 and MPY634:

(Note: TZA1047 is an IC of the DVD+RW drive.)

Please give any suggestions. Sorry that my scanned circuit diagram may not be very clear.

Thanks.

Thanks.

The "burnt" i meant is the IC is damaged. I could see some "sparks" come out. After the IC is being replaced, the drive becomes okay again?

Yup... the Vref voltage that's supposed to be ~1.945V would change to ~10V or above when we connected it to the external circuit.

I attach the link to my circuit diagram and also the drive's IC TZA1047 as below:

My design will take 5 voltage signals from the IC TZA1047, which are Vref, A, B, C and D. My circuit will first perform (A - Vref), (B - Vref), (C - Vref) and (D - Vref) (Note: Let A*= (A-Vref), B* = (B-Vref) and so on.)

Then, A*, B*, C* and D* will go into a circuit which does

Vout= [(A*+D*)-(B*+C*)]/(A*+B*+C*+D*)

The addition and subtraction part will be done by INA105kp while the division part will be done by mpy634.

(Note: TZA1047 is an IC of the DVD+RW drive.)

Please give any suggestions. Sorry that my scanned circuit diagram may not be very clear.

Thanks.

again?

Are you missing a ground connection? What about the INA105? Did you replace that as well? Maybe its inputs are blown.

Why don't you make a test harness consisting of resistive potential dividers, powered from the DVD. Connect your inputs to them (or it?) one at a time and make sure the voltage at the centre of the divider doesn't change. If it does, maybe that input has gone short circuit. This will also prove you have a sound ground reference.

TZA1047

Those links don't work for me; it redirects to the savefile home page.

may