RF2308
Pin
1
Function Description
Interface Schematic
RF input pin. This pin is NOT internally DC blocked. A DC blocking
RF IN
capacitor, suitable for the frequency of operation, should be used in
most applications. DC coupling of the input is not allowed, because this
will override the internal feedback loop and cause temperature instabil-
ity.
Ground connection. Keep traces physically short and connect immedi-
ately to ground plane for best performance.
2
GND
Same as pin 2.
3
4
5
6
7
8
GND
GND
GND
GND
GND
Same as pin 2.
Same as pin 2.
Same as pin 2.
Same as pin 2.
4
RF output and bias pin. Biasing is accomplished with an external series
resistor and choke inductor to V . The resistor is chosen to set the DC
RF OUT
CC
RF OUT
current into this pin to a desired level. At room temperature, this pin will
bias itself to 3.7V as long as the current is held between 20 and 65mA.
Thus the resistor value is determined by the following equation:
(VSUPPLY – 3.7)
F IN
----------------------------------------
R =
ICC
Care should also be taken in the resistor selection to ensure that the
current into the part never exceeds 65 mA over the planned oper-
ating temperature. This means that a resistor between the supply
and this pin is always required, even if a supply near 3.7V is available.
Because DC is present on this pin, a DC blocking capacitor, suitable for
the frequency of operation, should be used in most applications. The
supply side of the bias network should also be well bypassed.
Application Schematic
VCC = 5 V
10 nF
22 pF
47 nH
22
Ω
22 pF
RF IN
RF OUT
1
2
3
4
8
7
6
5
22 pF
Rev B2 010228
4-73
RFMD [ RF MICRO DEVICES ]
