MAX2630–MAX2633
VHF-to-Microwave, +3V,
General-Purpose Amplifiers
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_______________Detailed Description
The MAX2630–MAX2633 are broadband amplifiers with
3dB bandwidth greater than 1GHz. Their small size and
internal bias circuitry make them ideal for applications
where board space is limited. The MAX2632/MAX2633
have a user-selectable bias current that allows the user
to set both gain and output power for a particular appli-
cation, and the MAX2631/MAX2633 incorporate shut-
down capability.
__________Applications Information
External Components
The MAX2630–MAX2633 are easy to use, as shown in the
Typical Operating Circuit and Figures 1, 2 and 3. Input
and output series capacitors may be necessary to block
DC bias voltages generated by the amplifiers from inter-
acting with adjacent circuitry. These capacitors must be
large enough to contribute negligible reactance in a 50Ω
system at the minimum operating frequency. Use the fol-
lowing equation to calculate their minimum value:
where f (in megahertz) is the minimum operating
frequency.
The V
CC
pin must be RF bypassed for correct opera-
tion. To accomplish this, connect a capacitor between
the V
CC
pin and ground, as close to the package as is
practical. Use the same equation given above (for DC-
blocking capacitor values) to calculate the minimum
capacitor value. If the PC board has long V
CC
lines,
additional bypassing may be necessary. This can be
done farther away from the package, if needed.
Proper grounding of the GND pin is essential. If the PC
board uses a topside RF ground, connect it directly to
the GND pin. For a board where the ground plane is not
on the component side, the best technique is to con-
nect the GND pin to it with a plated through-hole close
to the package.
An on-chip buffer at the MAX2631/MAX2633’s SHDN
pin makes bypassing this pin unnecessary except in
very noisy applications. When RF filtering is needed,
use a bypass capacitor similar to the one used on V
CC
.
Since negligible current flows into this pin, additional
RF filtering may be done with a series resistor.
To set the MAX2632/MAX2633’s supply current,
connect a resistor from the BIAS pin to ground. To
estimate the value of this resistor, refer to the graph
Supply Current vs. R
BIAS
in the Typical Operating
Characteristics.
