max2235eup Maxim Integrated Products, Inc., max2235eup Datasheet - Page 6

• Manufacturer Part Number: max2235eup
• Description: 3.6v, 1w Autoramping Power Amplifier For 900mhz Applications Integrated Products
• Manufacturer: Maxim Integrated Products, Inc.

The MAX2235 power amplifier (PA) operates over a
wide frequency range of 800MHz to 1000MHz. The sig-
nal path consists of three stages: the input stage, the
driver stage, and the power stage. There are matching
circuits between the first and second stages, and
between the second and third stages. The bias circuits
process external commands to control the device’s
power-up/down and the gain of the PA.
The first stage is a variable-gain amplifier with 37dB
gain-control range. The input transistor acts as a
transconductor with constant bias current. Gain control
is achieved by steering the signal current from the input
transistor to the first output matching network (to drive
the second stage) or to a separate supply pin. This
+3.6V, 1W Autoramping Power
Amplifier for 900MHz Applications
6
SMA
_______________________________________________________________________________________
J1
V
CC
J3
J4
1000pF
V
CC
100pF
0.01 F
100pF
1000pF
Detailed Description
8.2nH
1 F
100pF
100pF
V
CC
22pF
Input Stage
10
1
2
3
4
5
6
7
8
9
RFIN
GND
V
V
V
GND
GND
V
V
GND
CC
CC
CC
CC
CC
MAX2235
stage operates in class A and remains on in standby
mode to ensure that the VSWR at the input does not
vary more than 1.5:1 compared with normal operation.
The input stage typically requires an external inductor
to achieve an optimum input VSWR.
The driver produces a signal large enough to drive the
power stage into saturation. The driver stage operates
in Class C and is off during standby.
The interstage matching networks provide optimal load-
ing and power transfer. The circuits are on-chip to save
board space. The bandwidths of the matching net-
works allow the PA to operate over a wide frequency
range.
RFOUT
RFOUT
RAMP
SHDN
*
GND
GND
GND
GND
REF
VALUE OF OUTPUT INDUCTOR DEPENDS ON APPLICATION.
GC
15
20
19
18
17
16
14
13
12
11
Second- and Third-Stage Matching
Typical Operating Circuit
*
0.068 F
47pF
470pF
1500pF
Second Stage (Driver)
470pF
11pF
1000pF
68pF
1000pF
JU2
V
CC
2
3
1
J2
JU1
SMA
V
CC