LMC662: High temperature opamp (> 200 Deg C) to replace LMC662

Ron Michallick,

plz  clarify the  following

1) you have shown signal source Cx in series with the fixed sensor capacitance C1 (250pF) in you circuit. please explain why?

2) to do the stability analysis should I consider the differential input  capacitance in parallel with common mode capacitance of non inverting terminal at the input of the opamp or will it be automatically factored by TINA-TI upon  selected the opa2333 model ?

3) for stability analysis should I use the approach as shown in below example for  breaking the loop and taking measurement?

4) Suppose I add an non inverting amplifier stage after the buffer(input stage).  The  Stability analysis for buffer and amplifier stages should be separately carried. out. is this approach correct ?

Regards

Kiran

Hi Kiran,

this could be your phase stability analysis:

kiran3.TSC

But don't forget to put your actual load (in parallel to RL) into the simulation!

Kai

Hi Kai,

Thanks for the advice!!

1) The original ckt has single supply, you have used dual. Is there any specific reason?

2) I have observed that single supply opamp is mostly operated by +5V  supply. Is there any disadvantage if I operate from a single -5V supply?

3) I am planning to add a non inverting amplifier after this stage. Should I add the input resistance/capacitance  as load or there is no need to add load?

4) While analyzing stability of the non inverting amplifier should I add C4,C5,R3 and RL at its non inverting input?

Regards

kiran

Hi Kiran,

I have given you the simulation file. So, check it out by yourself... :-)

Kai

Ron Michallick

Greetings

I have couple doubts from the above scheme you have suggested (single supply OPA2333)

1) upon switching on the 100V DC supply capacitor C2 charges to 100 V and later discharges. This will cause the opamp to see 100 V at the input. can I use zener diode (4.7V) to limit the voltage or is there any other effective solution.

2) Is ESD protection required at the input of the opamp?

3) If I want to add a non-inverting amplifier at the output of the opamp OPA2333 the DC reference (2.5 V) has to be added at the input of the non inverting amplifier again. This mean I have to use too many passive components. Is it better to use dual supply configuration or is there considerable advantage using  single supply configuration? 

4)  want to keep the amplifier noise as low as possible,  so planning to choose resistors in the range of ohms (100, 200, 300 ohms). But this will result in increased current consumption. Is it OK to do so or should I select resistors in the range of few Kilo ohms?

Ron Michallick,

Greetings !!

Thanks for the reply