MAX2235(1999) Ver la hoja de datos (PDF) - Maxim Integrated
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MAX2235 Datasheet PDF : 8 Pages
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+3.6V, 1W Autoramping Power
Amplifier for 900MHz Applications
Typical Operating Circuit
J1
SMA
100pF
8.2nH
VCC
1000pF
100pF
100pF
22pF
VCC
J3
1000pF
J4
0.01µF
1µF
100pF
VCC
1 RFIN
2
GND
GC 20
19
SHDN
3
VCC
4
VCC
5 VCC
GND 18
17
MAX2235 GND
RFOUT 16
6 GND
RFOUT 15
7 GND
GND 14
8 VCC
GND 13
9 VCC
REF 12
10 GND
RAMP 11
470pF
JU2
1000pF
VCC
470pF
3
2
JU1
1000pF 1
VCC
*
1500pF
68pF
J2
SMA
47pF
11pF
0.068µF
* VALUE OF OUTPUT INDUCTOR DEPENDS ON APPLICATION.
Detailed Description
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.
Input Stage
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
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.
Second Stage (Driver)
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.
Second- and Third-Stage Matching
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.
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