LTC 6268-10 The bandwidth seems to be different from the datasheet.

Hi

I turned to Bandwidth simulation in LTSPICE to use the LTC6268-10, but the result was different from the datasheet.

We want to implement a circuit with a bandwidth of 100MHz or more in the form of a transimpedance amplifier.

The LTC6268-10 datasheet states that 210MHz is possible with 20k ohms of RF, but the simulation results are quite different.

1. Can you tell me why?
2. Can you tell me what's wrong with my Spice setting?

    • The problem maybe not only about bandwidth but gain, the feedback capacitance is reducing the actual feedback impedance . The impedance of the 20kΩ is being reduced by its own parasitic capacitance and feedback capacitance at high frequency(see datasheet p.14). 
    • Try C2 around 0.1pF.Also with C1 1.1pF and 6268's input capacitance 0.45pF The bandwidth limit is about 140MHz.
  • 0
    •  Analog Employees 
    on Nov 26, 2018 5:15 PM

    Hi,

    You could also try our photodiode tool wizard in this link to help you design TIA's.

    I tried to use the tool and plugged in the values from your circuit above. I just change Ipd from 500uA to 50uA to fit into the limits set by the tool.

    I attached the exported files from this tool including the LTSPICE simulation.

    Take note also from page 13 of the datasheet the requirement of Cin/Cf>=10. The table1 was provided for the min and max values of Cf for Rf=20k and Cin=1pF.

    LTC6268-10.zip