The bandwidth of a photodetector is defined as :
MH SET - 2021, SET Exam - 2021,
Answer: B
The bandwidth is \([2\pi(\tau_{tr} + \tau_{RC})]^{-1}\).
The response speed of a photodetector is limited by the transit time of carriers across the depletion region, \(\tau_{tr}\), and by the RC time constant of the diode capacitance and load, \(\tau_{RC}\). Treating their sum as a single time constant gives a first-order cut-off frequency
\[ B = \frac{1}{2\pi(\tau_{tr} + \tau_{RC})} \]
The other options are not a frequency: one subtracts 1 from a time, one is the time constant itself, and one adds a dimensionless 1 to a time before inverting.
Please log in or register to report this question.