Valiant
Newbie level 5
Everybody:
We used a Maxim 2507 transmitter in our cellular phone.
There is a Saw filter between VGA and PA. Both the output of VGA and the input of PA are matched to 50ohm on chip. The output and input impendance are also 50ohm. In the reference design, There are two capacitances in the connection between the output of VGA and input of SAW, and the connection between the output of SAW and input of PA. One is 220pF, the other is 2.2pF.
I cannot understand the role the capacitance are playing and why the value of capacitances are not identical.
We used a Maxim 2507 transmitter in our cellular phone.
There is a Saw filter between VGA and PA. Both the output of VGA and the input of PA are matched to 50ohm on chip. The output and input impendance are also 50ohm. In the reference design, There are two capacitances in the connection between the output of VGA and input of SAW, and the connection between the output of SAW and input of PA. One is 220pF, the other is 2.2pF.
I cannot understand the role the capacitance are playing and why the value of capacitances are not identical.