2-21
RF2105L
Rev B3 010720
2
Pin
Function
Description
Interface Schematic
1VCC2
Positive supply for the second stage (driver) amplifier. This is an
unmatched transistor collector output. This pin should see an inductive
path toAC ground(VCC with a UHF bypassing capacitor). This induc-
tance can be achieved with a short, thin microstrip line or with a low
value chip inductor (~2.7nH). At lower frequencies, the inductance
value should be larger (longer microstrip line) and VCC should be
bypassed with a larger bypass capacitor (see the application schematic
for 430MHz operation). This inductance forms a matching network with
the internal series capacitor between the second and third stages, set-
ting the amplifier’s frequency of maximum gain. An additional 1
µF
bypass capacitor in parallel with the UHF bypass capacitor is also rec-
ommended, but placement of this component is not as critical. In most
applications, pins 1, 2, and 3 can share a single 1
µF bypass capacitor.
2VCC3
Positive supply for the active bias circuits. This pin can be externally
combined with pin 3 (VCC1) and the pair bypassed with a single UHF
capacitor, placed as close as possible to the package. Additional
bypassing of 1
µF is also recommended, but proximity to the package is
not as critical. In most applications, pins 1, 2, and 3 can share a single
1
µF bypass capacitor.
3VCC1
Positive supply for the first stage (input) amplifier. This pin can be exter-
nally combined with pin 2 (VCC3) and the pair bypassed with a single
UHF capacitor, placed as close as possible to the package. Additional
bypassing of 1
µF is also recommended, but proximity to the package is
not as critical. In most applications, pins 1, 2, and 3 can share a single
1
µF bypass capacitor.
4GND
Ground connection. For best performance, keep traces physically short
and connect immediately to ground plane. In addition, for specified per-
formance, the package’s backside metal should be soldered to ground
plane.
5PD
Power down control voltage. When this pin is at 0V, the device will be in
power down mode, dissipating minimum DC power. When this pin is at
VCC (3V to 6.5V), the device will be in full power mode delivering maxi-
mum available gain and output power capability. This pin may also be
used to perform some degree of gain control or power control when set
to voltages between 0V and VCC. It is not optimized for this function so
the transfer function is not linear over a wide range as with other
devices specifically designed for analog gain control; however, it may
be usable for coarse adjustment or in some closed loop AGC systems.
This pin should not, in any circumstance, be higher in voltage than VCC,
nor should it ever be higher than 6.5V. This pin should also have an
external UHF bypassing capacitor.
6RF IN
Amplifier RF input. This is a 50
Ω RF input port to the amplifier. It does
not contain internal DC-blocking and therefore should be externally
DC-blocked before connecting to any device which has DC present or
which contains a DC path to ground. A series UHF capacitor is recom-
mended for the DC-blocking.
7GND
Same as pin 4.
8NC
Not internally connected.
9NC
Not internally connected.
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