LMC6041: LMC641IMX/NOPB

Hello,

Could you please take a picture of the top side markings for both parts and place them here?

How much input bias current are you seeing?  Could you please tell us how you are configuring your setup/circuit?

This information will help us to resolve your issue.

Regards,

Daniel

Hello,

I have not heard back from you in a while.  Please let me know if you need any further assistance, else I will consider your issue to have been resolved.

Thanks,

Daniel

I have sent you an email at Jan. 17.But not got any reply massage of resolve the problem.

Here I attach that email and the 4 pictures which attached in that email.

Following is the email:

"Here attach 4 pictures to you:

1.top side of the PHI made IC;

2.top side of the LMA made IC,

3.packing with order label;

4.test circuit.

according to our measurement,the Ib of LMA made IC is under 20 fA,while PHI made is above 5 pA.

So, the PHI IC can't be used in our products.

By the way, the outlook of the them are different,the hole on the top side  of LMA is larger.I don't know why?

Please replace this IC with a good quality products.If there are any problem,please let me know.

Best regards,

Xuxian"

I appreciate to your reply ASAP.

Best regards,

Xuxian6041.zip

Hello Xuxian,

My apologies, but I checked my inbox, deleted messages, and junk email and could not find your email anywhere.  I have sent you an invitation to connect and, if you accept it, you should be able to email me directly with any further assistance that you may need with this question.

I have spoken with my colleague about this matter and we have determined that the circuit you are using to measure the bias current will not work for a CMOS device because the bias current measurement needed will be too small.  This concept is explained in more detail by Marek Lis and Paul Grohe, two experienced applications engineers, in this e2e post.  Here, they cover the subject of measuring very small bias currents.  They also provide a better circuit for measuring the bias current.  When building this circuit, you could use a relay for a switch.

I would recommend you use this circuit to get a more accurate measurement for I_bias.  This will allow us to determine with greater confidence the performance of the parts.  Images of results would also help.

I would be happy to assist you in this process.  Please let me know if you have any further questions or need any help.

Best regards,

Daniel

Dear Daneil,

The circuit which Toshi provided is no use in measuring fA Iib current. Because, it's Rf is too small, Not enough sensitive.

The method which Paul Grohe mention about is based on the voltage increaing on an integrated capacitor. We had also used this method to measure the Iib. Compare to our circuit, the test result are the same. But our  test circuit is based on high resistance sampling resistor and is easy to operate.

In fA current  measurement, PCB resistance is an important problem. To avoid the leakage current  caused by PCB, We prefer to let the input terminal of the amplifier IC stay in the air, but not soldering to PCB. So, the relay you suggested might not be a good idea. Because it's resistance should be  upto 10e15 OHM. It is very difficult to find this kind of relay.

Any way, our measurement shows, the quality problem of the SO# T00596094, IC LMC6041, is quite obvious. The Iib of LMA made IC is below 20 fA, while  the PHI made IC is above 5PA,They have a big difference. This quality is not agree to the product specification  of TI. They can’t be USED in our products. Since the Iib parameter can’t  meet  our requirement also can’t meet TI standard, We request TI to replace this lot of IC from  PHI made IC  to LMA made.

Best regards,

Xuxian

Hello Xuxian,

I agree that the Toshi method is insufficient.

You say, "The method which Paul Grohe mention about is based on the voltage increaing on an integrated capacitor. We had also used this method to measure the Iib. Compare to our circuit, the test result are the same."

Can you please share your results showing the capacitor discharge?  

Regards,

Daniel

Below response is from Xuxian, I helped transfer to you. 

Dear Daneil,
Here attach the test circuit and result of our measurement by using “Capacitor charging” method。In the measurement, we used a special switch. It is made by myself, The insulation resistance is 10e18 OHM. So this measurement is quite accurate. Though it need more test time. Compare to this method, the “resistance increasing voltage” method is much quickly and easy to operate. The test result of these 2 method are the same. From our test result, you may see the large different between the LMA made IC and PHI made. About 250 times.
I like to know your view on our measure result. Also, I hope you may help us to replace the PHI made IC with LMA made or some other with good Iib amplifier chip.
Thanks and best regards,
Xuxian

Hello Alex and Xuxian,

Thank you for your response and test results.

Unfortunately, I cannot see the measurements as the attachment was not made.

Can you please reattach the results of your measurements with a schematic.  I will be happy to take a look and offer my help.

Regards,

Daniel

How many PHI devices samples indicate this high IIB current. Do all PHI samples indicate high current?  

I'm curious if the high IIB is also present on the IN- pin. Ground input and move capacitor to feedback, OUT to IN- 

Part Number: LMC6041

Dear Daneil,

Following picture is the test circuit and result of our measurement by using “Capacitor charging” method。In the measurement, we used a special switch. It is made by myself, The insulation resistance is 10e18 OHM. So this measurement is quite accurate. Though it need more test time. Compare to this method, the “resistance increasing voltage” method is much quickly and easy to operate. The test result of these 2 method are the same. From our test result, you may see the large different between the LMA made IC and PHI made. About 250 times.

I like to know your view on our measure result. Also, I hope you may help us to replace the PHI made IC with LMA made or some other with good Iib amplifier chip.

Thanks and best regards,

Xuxian

Ron,

Xuxian opened a second thread on the same issue.  I am combining the threads here.

Here are the extra comments he added for the above results: 

Following picture is the test circuit and result of our measurement by using “Capacitor charging” method。In the measurement, we used a special switch. It is made by myself, The insulation resistance is 10e18 OHM. So this measurement is quite accurate. Though it need more test time. Compare to this method, the “resistance increasing voltage” method is much quickly and easy to operate. The test result of these 2 method are the same. From our test result, you may see the large different between the LMA made IC and PHI made. About 250 times.

I like to know your view on our measure result. Also, I hope you may help us to replace the PHI made IC with LMA made or some other with good Iib amplifier chip.

Thanks and best regards,

Xuxian

Dear Ron Michallick,

All the PHI made devices indicate high IIB current. I had test both IN+ pin and IN- pin input terminals, the same result, high IIB.In IN- pin test, I used the method as you mentioned about, Ground IN+ and move capacitor to feedback, OUT to  IN_pin,short or open the capacitor,then caculate the IIB by the voltage difference.
I think,maybe this problem is caused by the leakage of the chip packing material.
I only used IN+ in my products,but the high IIB current device is not allowed.I had  also compared the PHI device with LMA device,a large difference in IIB,about 250 times.

So,please replace the PHI made with LMA made to me.

Thanks and best regards,

Xuxian

Xuxian,

Where did you buy the reel (D=1903)?  Have you requested a return authorization?

Accept my friend request , If you would like to discuss this privately.

I bought that reel from Singapore, “Texas Instrument southeast Asia PL，TI eCommerce PDC Sgp (Hub)".I want TI to replace the PHI chip with LMA,or return the devices and refund me. But I have not provided the authorization.I don't know how to operate?Can you help me?

If you bought directly from Texas instruments start here  :https://ticsc.service-now.com/csm/

e2e is engineering forum. I do not have direct access to return process.

I did check to see if there was a orderable part number variant that would only ship the "LMA" and I did not find one.