I am designing a transimpedance amplifier using LTC6268-10 from Analog Devices. The photodiode that I use is S9055-01 from Hamamatsu and the laser source that I use has a power of 10mW with the wavelength of 660nm. The laser is a pulsed source with frequency of 50KHz and the pulse width is 1ns. By using the responsivity value(0.35A/W) of the photodiode and the laser power value(10mW), I have calculated the output current of the photodiode to be 3.5mA using below formula
photodiode current = responsivity X laser power
The output voltage from the amplifier should be 1.3V. So I have used these current and voltage values to determine the feedback resistor and capacitor values using the formulae below
The frequency value that I have used in the formula to find the capacitance value is 1GHz since the pulse width of the laser source is 1ns. The input source capacitance i.e. the junction capacitance of the photodiode is 0.5pF. The common mode capacitance and differential mode capacitance of LTC6268-10 are 0.45pF and 0.1pF respectively. So the Ci value is 1.05pF(0.5 + 0.45 + 0.1). The resistance and capacitance values that I've got from the calculation are 371Ω and 0.428pF respectively. Also the GBW value that I've got from the formula is 3.45Ghz which is below the maximum GBW of LTC6268-10. Are these values correct? Or should I modify the calculation to get the correct values? I have attached the datasheets of LTC6268-10 and Hamamatsu S9055-01 below
LTC6268-10 datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/626810f.pdf
Hamamatsu S9055-01: https://www.hamamatsu.com/content/dam/hamamatsu-photonics/sites/documents/99_SALES_LIBRARY/ssd/s9055_series_kpin1065e.pdf
Thanks in advance!