LF411: design parameters for BAL 1 and BAL2 pins

Renan Santos Adriano

Mastermind 20490 points

Part Number: LF411

Hello Team,

Good day.

My customer is looking for design parameters for BAL1 and BAL2 pins for the LF411 device. The datasheet has limited information on these pins, can you share any information we can use?

Regards,

Renan

over 4 years ago

0 Ron Michallick over 4 years ago

TI__Guru**** 157416 points

Hello Renan,

The balance pins connect to the input stage resistors that terminate to VCC- pin. Typically an external potentiometer wiper connects to VCC- and the two ends go to BAL1, BAL2.

The LF411 is very old device, we have better modern devices for new applications.

0 Renan Santos Adriano over 4 years ago in reply to Ron Michallick

TI__Mastermind 20490 points

Hello Ronald,

Good day and thank you for this response.

My customer really wanted to use this device and wanted to know further about these pins. Is there a recommended value for the external potentiometer? As well as, is there a correlation or equation that represents the values or trimming of the external potentiometer?

Regards,

Renan

0 Ron Michallick over 4 years ago in reply to Renan Santos Adriano

TI__Guru**** 157416 points

Renan,

I have some LF411 samples in stock. I will measure the internal resistance so I can suggest an external pot value.

Answer in about two days.

0 kai klaas69 over 4 years ago in reply to Renan Santos Adriano

Guru 140200 points

Hi Renan,

this appnote recommends a 10k trimmer:

AN-447 Protection Schemes for BI-FET Amplifiers and Switches

Kai

0 Ron Michallick over 4 years ago in reply to Renan Santos Adriano

TI__Guru**** 157416 points

Renan,

A 10k pot does work, but it is too powerful. the op amp output can be forced to VOL or VOH if the pot is turned too close to either end.

Adding 22k resistors to the pot ends helped. With this, the tuning range was +/-6.8mV. Make R2,R3 bigger to reduce the range or make them smaller to increase the tuning range. 12.7k was +/-15.3mV

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LF411: design parameters for BAL 1 and BAL2 pins