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THS3121: New and alternative OPAMP parts

d_zero
Genius 4855 points
Part Number: THS3121
Other Parts Discussed in Thread: THS3470, THS3491, , OPA891, OPA2675

Dear Team,

 

we have  a 10+ year old shematic that uses varius OPAMPS, we would like to select newer and better devices, please can you propose newer devices for following 

 

1) THS3121ID , can you propose VF OPAMP with good transient preofmance and low noise? 

2) LT1028CS8#PBF

3)LT1210CS#PBF 

The OPAMPS are used as unity gain buffers for image sensor BIAS supply.

 

Best Regards,

d.

  • 0
    TI__Genius 17675 points

    Hi,

    For the potential replacement of the THS3121, can you share what kind of slew rate or large signal bandwidth requirements are needed? This will help zero in on VFB devices that could work with your system. Regarding the LT1028, the part we recommend is the OPA891. This is one of our lower noise devices with good speed that has similar functionality to the competitor device. For the LT1210, a close competitor would be the OPA2675, however the supply voltage might not be high enough depending on your setup for the LT1210. We also have the THS3491, which is a 30V device with very good large signal bandwidth however the output current is limited compared to the competitor device. One device that meets both the supply voltage and current requirements is our new THS3470 device. It is a lot more involved and has performance specs that are much higher than the competitor, but this does meet supply and current demands you might require. If there is any additional information on what specs are more important for you, we can zero in on potential devices.

    Best Regards,

    Ignacio

  • 0 in reply to Ignacio Vazquez Lam1
    Genius 4855 points

    Hi Ignacio,

    thank you for the answer, i'm still waiting for the BIAS specifications ( transient peak current and time). In the mean time here is what i know:

    1) THS3121 , we can go with VF or CF opamp

    -> This  opmap is powered with v+ = +5V and  v- = 0V

    -> The output voltage ripple should be < 30uV Vpp ( ~ 5uV Vrms)

    -> We should go with similar Iout and slew rate spec

    -> I think here we can also use the OPA2675, what do you think?

    2) and 3) In some  app note the two opamps LT1028CS8#PBF and LT1210CS#PBF  are cascaded but i'm not shore why.

    -> DAC output voltage (-0.7V) -> unity gain buffer  LT1028CS8#PBF -> unity gain buffer LT1210CS#PBF -> BIAS pin of the sensor.

    -> booth opamps  are supplied with V+ = +4V , V- = -3.3V

    > The output voltage ripple should be < 30uV Vpp ( ~ 5uV Vrms)

    -> I think we can use OPA2675 instead of LT1210 ( current output similar, noise performance a little better , slew rate better ...) , what do you think?

    -> I don't know if we need to use something instead of LT1028 , maybe it is because of needed low noise?

     

    Please let us know your thoughts.

    I can share the schematic in DM, let me know.

    Best Regards,

    d.