2021 Solution 11
2021 Solution 11
Isaac P Abraham
2020 Dec 25
2020 Dec 25
Consider the T-coil used to implement bandwidth extension. Let RD << .
rds
M1
What is the ratio of the output impedance at very high frequencies to very low frequencies? In other words, =?
Z(out)
|
ω∞
Z(out)
|
ω0
At very low frequencies, the inductors short out the capacitor CB. The resulting output impedance is RD.
At very high frequencies, although the inductors present a high impedance, the opposed magnetic coupling ensures that the signal sees RD//. The resulting output impedance is ~RD.
At very high frequencies, although the inductors present a high impedance, the opposed magnetic coupling ensures that the signal sees RD//
rds
M1
The desired ratio is 1.