Low-Cost, 900MHz, Low-Noise Amplifier

and Downconverter Mixer

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9

Local-Oscillator Input

The LO port is the high-impedance input of the local-

oscillator buffer. It requires a series DC-blocking

capacitor and a shunt resistor to ground to set the input

impedance. See the

Typical Operating Characteristics

for a graph of LO Port Return Loss vs. Frequency.

IF Output Port

The mixer’s downconverted output appears on the dif-

ferential IFOUT+ and IFOUT- pins. The differential out-

put can be converted to a single-ended output, as

shown in the MAX2685 evaluation kit (EV kit). Refer to

the

Detailed Description in the MAX2685 EV kit data

sheet.

Shutdown

Drive SHDN low to disable all device functions and

place the MAX2685 in low-power shutdown mode.

device functions.

Applications Information

Layout Considerations

A properly designed PC board is an essential part of

any RF/microwave circuit. Note the IC’s high-frequency

inputs and outputs, and be sure to decouple the DC

supply and control pins.

For power-supply traces and connections, a star topol-

capacitor that provides a low impedance at the RF fre-

decoupling capacitor. This provides good isolation

between the different sections of the MAX2685.

Chip Information

TRANSISTOR COUNT: 295