The Wave are the input and out waveform of the LF357N，but  TLE2071 has not output  waveform.

Hi Zewei,

this circuit looks very very strange to me.

When powering the LF357 in single supply mode and connecting the +input to signal ground you heavily violate the common mode input voltage range of LF375, as you must stay 4V away from the supply rails.

And connecting a cap at the -input of LF357, or by other words providing AC coupling, even forces the potential of -input going below the negative supply voltage. By this you even risk the destruction of chip.

I don't think that this circuit is correct.

Kai

The input common mode can't be ground It should be a t least 4V. Do you want the gain to be 10,000 (1M/100)? If yes, why is the input so large? Connect IN+ to a higher voltage.

Hi Ron,

I guess the LF357 is wired as fast slewing comparator using a dummy gain of 10000. There are many legacy circuits arround using this "technique".

Kai

You are right ! But   TLE2071 has not output signal.Please  help me , thank  you  very much !

But   TLE2071 has not output signal.Please  help me , thank  you  very much !

Zewei,

Bring pin 3 up to 4V which is a valid input common mode voltage. Then the op amp will work.

An alternative is to use a different op amp that allows input voltage down to ground. If interested, provided the full TLE2071 part number so I can search correctly.