at86rf211 ATMEL Corporation, at86rf211 Datasheet - Page 14

• Manufacturer Part Number: at86rf211
• Description: Fsk Transceiver For Ism Radio Applications
• Manufacturer: ATMEL Corporation

IF2 Amplifier Chain
14
AT86RF211
Figure 16. LC Band-pass Filter
•
•
•
The input impedance of the IF2 amplifier is 1700 . This value enables the use of popu-
lar filters with impedance between 1500 and 2000 . It is directly connected to the FSK
demodulator. The bandwidth is internally limited to 1 MHz to minimize the noise before
the discriminator. It acts like a band pass filter centered at 455 kHz with capacitive cou-
pling between stages of amplifier and mixer. Total voltage gain is typically 86 dB.
Thanks to the capacitive coupling, no slow DC feedback loop is needed enabling a fast
turn on time. IF2DEC has to be decoupled with at least 2.2 nF.
Figure 17. Input of the IF2 Amplifier Schematic
10 nF capacitors cut DC response forward and backward.
The first network has the low cut-off frequency.
The second network has the high cut-off frequency.
Filter
gain
IF2DEC
IF2IN
10 nF
~ F1
40 kHz or higher
F1
F2
~ F2
1900
global response
10 nF
Frequency
1942C–WIRE–06/02