Op-amp buffer

[Akshatha Venkatesh]

The below circuit is a current measurement circuit , the mosfet is always on in my application and the volatge across the shunt 100k is measured and given to ADC pin of uC.cananyone explain the function of the Opamp as voltage follower in the circuit ? What would happen if the opamp wasn't present ? The current at IDE- is 45V/45Mohm= 10 micro amp.

 

[Audioguru]

The opamp has a high impedance input so that it does not overload the filtered input signal and it has a powerful output that can drive a low impedance output circuit that is not shown.

How can the opamp drive a circuit not shown that has 45V? Maybe the output of the opamp clamps the 45V to its maximum lower voltage output?

 

[Akshatha Venkatesh]

The opamp has a high impedance input so that it does not overload the filtered input signal and it has a powerful output that can drive a low impedance output circuit that is not shown.

How can the opamp drive a circuit not shown that has 45V? Maybe the output of the opamp clamps the 45V to its maximum lower voltage output?

Sorry , I don't understand . I've mentioned the 45V only to give an idea of the current being measured.

 

[Audioguru]

The load for the opamp is not shown so we do not know why the opamp is needed. The input of the opamp has a high impedance lowpass filter and the output of the opamp has a lower impedance lowpass filter that feeds the unknown load.

 

[WHONOES]

Can you show the rest of the circuit including the input load and whatever the opamp is driving?

 

[Akshatha Venkatesh]

The load for the opamp is not shown so we do not know why the opamp is needed. The input of the opamp has a high impedance lowpass filter and the output of the opamp has a lower impedance lowpass filter that feeds the unknown load.

the load for the opamp is the microcontroller ADC pin.

 

[Akshatha Venkatesh]

Can you show the rest of the circuit including the input load and whatever the opamp is driving?

the input load is a sensor probe element (PTC), the opamp is driving the microcontroller ADC input.

 

[Akshatha Venkatesh]

Can you show the rest of the circuit including the input load and whatever the opamp is driving?

Hi, could you help me on this