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MAX2057

1700MHz to 2500MHz Variable-Gain Amplifier with Analog Gain Control

Maxim Integrated 

1700MHz to 2500MHz Variable-Gain

Amplifier with Analog Gain Control

Table 1. Typical Application Circuit

Component Values

DESIGNATION

C1, C3, C5, C7, C10

VALUE

22pF

TYPE

Microwave capacitors

(0402)

C2, C4, C6, C8, C9

1000pF Microwave capacitors

(0402)

C13, C14, C15

0.1µF Microwave capacitors

(0603)

C17

0.75pF Microwave capacitor

(0402)

R1

1.2kΩ ±1% resistor (0402)

R2

2kΩ ±1% resistor (0402)

Applications Information

Analog Attenuation Control

A single input voltage at the VCNTL pin adjusts the gain

of the MAX2057. Up to 21dB of gain-control range is

provided through a single attenuator. At the maximum

gain setting, each attenuator’s insertion loss is approxi-

mately 2.2dB. With the single attenuator at the maximum

gain setting, the device provides a nominal 15.5dB of

cascaded gain and 6dB of cascaded noise figure.

If a larger gain-control range is desired, a second on-

chip attenuator can be connected in the signal path to

provide an additional 21dB of gain-control range. With

the second attenuator connected at the maximum gain

setting, the device typically exhibits 13.3dB of cascad-

ed gain. Note that the VCNTL pin simultaneously adjusts

both on-chip attenuators.

The VCNTL input voltage drives a high-impedance load

(>250kΩ). It is suggested that a current-limiting resistor

be included in series with this connection to limit the

input current to less than 40mA should the control volt-

age be applied when VCC is not present. A series resis-

tor of greater than 200Ω will provide complete

protection for 5V control voltage ranges. Limit VCNTL

input voltages to a 1.0V to 4.5V range when VCC is

present to ensure the reliability of the device.

Amplifier Bias Current

The MAX2057 integrates a two-stage amplifier to simul-

taneously provide high gain and high IP3. Optimal per-

formance is obtained when R1 and R2 are equal to

1.2kΩ and 2kΩ, respectively. The typical supply current

is 180mA and the typical output IP3 is 37dBm under

these conditions.

Increasing R1 and R2 from the nominal values of 1.2kΩ

and 2kΩ reduces the bias current of each amplifier

stage, which reduces the total power consumption and

IP3 of the device. This feature can be utilized to further

decrease power consumption for applications that do

not require high IP3.

Layout Considerations

A properly designed PC board is an essential part of

any RF/microwave circuit. Keep RF signal lines as short

as possible to reduce losses, radiation, and induc-

tance. For best performance, route the ground-pin

traces directly to the exposed pad underneath the

package. This pad MUST be connected to the ground

plane of the board by using multiple vias under the

device to provide the best RF and thermal conduction

path. Solder the exposed pad on the bottom of the

device package to a PC board exposed pad.

Power-Supply Bypassing

Proper voltage-supply bypassing is essential for high-

frequency circuit stability. Bypass each VCC pin with

capacitors placed as close to the device as possible.

Place the smallest capacitor closest to the device. Refer

to the MAX2057 evaluation kit data sheet for more details.

Exposed Paddle RF and Thermal

Considerations

The EP of the MAX2057’s 36-pin thin QFN-EP package

provides a low-thermal-resistance path to the die. It is

important that the PC board on which the IC is mounted

be designed to conduct heat from this contact. In addi-

tion, the EP provides a low-inductance RF ground path

for the device.

The EP MUST be soldered to a ground plane on the PC

board either directly or through an array of plated via

holes. Soldering the pad to ground is also critical for

efficient heat transfer. Use a solid ground plane wher-

ever possible.

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