MAX2472EUT-T 查看數據表（PDF） - Maxim Integrated

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MAX2472EUT-T

500MHz to 2500MHz VCO Buffer Amplifiers

Maxim Integrated 

500MHz to 2500MHz

VCO Buffer Amplifiers

VCC

(PIN 6)

VCC

(PIN 6)

IN

(PIN 4)

1.3pF

1k

GND

(PIN 5)

Figure 1. Input Structure

VCC

(PIN 6)

2k

250Ω

33Ω

OUT

10Ω

GND

(PIN 2)

Figure 2. Output Structure

Applications Information

Input Considerations

The MAX2472/MAX2473 offer high-impedance inputs

ideal for low-distortion buffering of a VCO. For applica-

tions with discrete transistor-based oscillator designs,

simply AC-couple the oscillator directly to the input; the

buffer’s high input impedance results in minimal load-

ing on the oscillator. For use with 50Ω VCO modules,

determine the approximate input impedance (S11) of

INTERNAL

1.2V

REFERENCE

1k

BIAS

(PIN 3)

GND

(PIN 2)

Figure 3. BIAS Structure (MAX2473 only)

the MAX2472/MAX2473 from the S parameter tables in

the Typical Operating Characteristics. Terminate the

buffer input with a shunt resistor “RTERM” such that

RTERM || RE[S11] = 50Ω, and use a series blocking

capacitor between the shunt resistor and the device

input. This provides a very stable 50Ω termination and

increases reverse isolation. For those applications

needing both high gain and good input match, reac-

tively match the buffer inputs to 50Ω with simple two-

element matching circuits. Figure 1 shows an equivalent

input circuit of the MAX2472/MAX2473 IN pin.

Output Considerations

The MAX2472/MAX2473 outputs are configured as

open-collector output stages, allowing maximum flexi-

bility. To achieve maximum gain and output drive, reac-

tively match these outputs with a shunt inductor/choke

to VCC followed by a series capacitor (DC block). For

applications not requiring high gain and output drive

(PLL prescaler), use a simple resistor to VCC followed

by a DC blocking capacitor. Figure 2 shows an equiva-

lent circuit of the MAX2472/MAX2473 OUT pin(s).

Figure 3 shows an equivalent circuit of the MAX2473

BIAS pin.

Output Matching Circuit

Table 1 lists recommended values for lumped-element

output matching circuits at certain frequencies. For fre-

quencies other than those specified, use the parame-

ters given in the Typical Operating Characteristics.

Layout and Power-Supply Bypassing

A properly designed PC board is essential to any

RF/microwave circuit. Be sure to use controlled imped-

ance lines on all high-frequency inputs and outputs.

Bypass the power supply with decoupling capacitors

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