10Gbps Optical Receiver and VCSEL Driver in 0.13um CMOS ...

Fig 2.3 shows the AC equivalent circuit for PIN PD. The value of
parasitic components can be estimated to C PD =0.15~0.25-pF and
R S =20Ω for 10-Gb/s operation. We can see that the output impedance
of the p-i-n photodiode is mostly capacitive [8].
Figure 2.3 AC Equivalent Circuit for p-i-n Photodiode
2.1.2 Transimpedance Amplifier
2.1.2.1 TIA Specifications
Before looking into the implementation of TIAs, it is useful to
discuss their main specifications: the transimpedance gain (Z T ), the
bandwidth, the input-referred noise current.
Transimpedance Gain (Z T )
The transimpedance gain (Z T ) is defined as the output voltage
change, ∆Vout, per input current change, ∆Iin (See Fig 2.4):
Z
ΔV
out
T
= (2.3)
ΔI
in
8