AOP

Question

Hello, 
 I would like to find a equivalent with this component 'LT6233CS6#TRMPBF' because i have to order 5000 pieces. Do you know any components with the same footprint and the same function pins because I have already designed the PCB. 
 Thank for your helps 
 Regards

Hooman · Answer

Hi 206_RC , 
 I recommend that you take a look at the Filter Wizard program link below to design your High Pass filter using LT6233: 
 https://tools.analog.com/en/filterwizard/ 
 Let me know if you have any specific question regarding this design. 
 Regards, 
 Hooman

Hooman · Answer

Hi 206_RC , 
 Regarding the offset you're seeing from using LT6233 as a Sallen Key High Pass Filter: 
 Most of that is due to the input bias current of LT6233 (3uA max) flowing through the 22.5kohm input resistor (R1). 
 I've added a dummy current source to your schematic to allow you to change that current and see the output offset go away or increase (depending on the magnitude and direction of that current). 
 
 Here is the simulation file: 
 LT6233 Sallen Key Filter Offset EZ 7_11_22.asc 
 To resolve this issue, you can do one or both of the following: 
 1. Scale your R's lower and your C's higher (to maintain the same filter response) by the same factor (e.g. 22.5k ->2.25k and 1uF --> 10uF, etc.) to reduce the impact of input bias current on output shift. 
 2. Switch to another Op Amp with CMOS / JFET input structure where the input bias current reduces to the pA range. Let me know if you need help selecting a usable device? 
 Additionally, I added a shunt resistor to your 2nd stage (R3) to allow for input bias current flow. 
 Regards, 
 Hooman

Hooman · Answer

Hi 206_RC , 
 
 206_RC said: Sorry to bother you but I'm still looking for a -1.5µA current source and haven't found it yet. 
 
 Response : The -1.5uA current source I added was only there to demonstrate that the input bias current of LT6233 (about 1.5uA in its model) is responsible for your output offset. Once I added the -1.5uA current source, I was able to null the output offset. So, that's why I recommended choosing a device with CMOS / JFET inputs where the input current is in the pA or nA range (much lower) so that you won't have this offset. 
 
 Regards, 
 Hooman

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