TDA5255E1_07 Datasheet, PDF (41/91 Pages) Infineon Technologies AG – ASK/FSK 434MHz Wireless Transceiver

TDA5255 E1
Version 1.2
Application
Now both pin-diodes are biased with a current of approx. 0.3mA@3V and have a very low
impedance for RF.
TX_Mode.wmf
Figure 3-4 TX_Mode
R1 does not influence the matching because of its very high resistance. Due to the large
capacitance of C1, C6 and C5 the circuit can be further simplified for RF:
TX_Mode_simplified.wmf
Figure 3-5 TX_Mode_simplified
The LNA-matching is RF-grounded now, so no power is lost in the LNA-input. The PA-matching
consists of C2, C3 L2, C4 and L1.
When designing the matching of the PA, C2 must not be changed anymore because its value is
already fixed by the LNA-input-matching.
Data Sheet
41
2007-02-26