Rainbow-electronics MAX2130 Manual do Utilizador descarregar pdf (Página 7)

Dynamic Linearity Adjustment

The LNA and loop-out amplifier linearity can be dynam-

ically adjusted by varying the amount of current

sourced by the BIAS port. The BIAS port is internally

biased to 1.2V. A resistor, R

BIAS

, connected from BIAS

to ground sets the bias current. An additional resistor,

ADJ

, placed from the BIAS port to an external voltage

source, such as a digital-to-analog converter (DAC),

varies the current sourced by the BIAS port. Choosing

ADJ

= R

BIAS

= 20kΩ and varying the voltage of the

DAC from ground to 2.4V effectively varies the resis-

tance seen from the BIAS port from 10kΩ to an open

circuit. See Typical Application Circuit.

The DAC output voltage, V

ADJ

, required to set an equiv-

alent resistance to ground, R

, seen by the BIAS port,

can be calculated with the following equation:

ADJ

= 2.4V - (R

BIAS

) / R

where R

ADJ

= R

BIAS

, V

BIAS

= 1.2V, R

≥ 10kΩ.

Power-Supply Bypassing

Proper voltage-supply bypassing is essential for high-

frequency circuit stability. Bypass the V

pin with a

1000pF capacitor in parallel with a 47pF capacitor,

located as close to the V

pin as possible. Refer to

the MAX2130 EV kit for additional information.

MAX2130

Broadband, Two-Output, Low-Noise

Amplifier for TV Tuner Applications

_______________________________________________________________________________________ 7

GND

OUT2GND

OUT1

GNDIN

BIAS

µMAX-EP

TOP VIEW

MAX2130

Pin Configuration

Chip Information

TRANSISTOR COUNT: 167

1 2 3 4 5 6 7 8

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