AD8367 datasheet(11/16 Pages) AD

11 / 16 page

REV. 0

AD8367

–11–

Table II. Reactive Matching Components for a 50

Ω System, R

S = 50

Ω, R

LOAD = 50

Ω

Frequency (MHz) XSIN

XPIN (pF)

XSOUT (pF)

XPOUT

1.5

120

180

1.8

220 nH

270 nH

140

120 nH

150 nH

190

82 nH

100 nH

240

68 nH

82 nH

Table I. S-Parameters for 50

Ω System for V

S = 5 V, and VGAIN = 0.75 V

Frequency (MHz)

S11

S21

S12

S22

0.64 0

8.5 177

× 10−3 153°

0.02 11

0.64 –1.5

9.0 168

× 10−4 106°

0.02 54

140

0.63 –3.0

10.0 152

× 10−4 80°

0.06 88

190

0.63 –3.7

10.4 138

× 10−4 147°

0.09 83

240

0.62 –4.9

10.8 125

× 10−3 148°

0.1 76

0.3333

–0.3333

–1

–3

0.3333

ZIN

RSOURCE

SERIES L

SHUNT C

140MHz, ZIN

193.4

j46.3 , ZLOAD

229

j8.8

RSOURCE

50 , RLOAD

RSOURCE

XPIN

5pF

XSIN

120nH

ZIN

ZOUT

CAC

0.1 F

XSOUT

13pF

XPOUT

150nH

RLOAD

AD8367

ZIN

ZLOAD

Figure 6. Reactive Matching Example for f

140 MHz

APPLICATIONS

The AD8367 can be configured either as a variable-gain amplifier

whose gain is controlled externally through the GAIN pin or as an

AGC amplifier, using a supply voltage of 2.7 V to 5.5 V. The

supply to the VPSO and VPSI pins should be decoupled using a

low-inductance 0.1 F surface-mount ceramic capacitor, as close

to the device as possible. Additional supply decoupling may be

provided by a small series resistor. A 10 nF capacitor from pin

DECL to OCOM is recommended to decouple the output refer-

ence voltage.

Input and Output Matching

The AD8367 is designed to operate in a 200

Ω impedance sys-

tem. The output amplifier is a low output impedance voltage

buffer with a 50

Ω damping resistor to desensitize it from load

reactance and parasitics. The quoted performance includes the

voltage division between the 50

Ω resistor and the 200 Ω load.

The AD8367 can be reactively matched to an impedance other

than 200

Ω using traditional step-up and step down matching

networks or high quality transformers. Table I lists the 50

Ω

S-parameters for the AD8367 at a VGAIN

750 mV.

Figure 6 illustrates an example where the AD8367 is matched to

Ω at 140 MHz. As shown in the Smith Chart, the input match-

ing network shifts the input impedance from ZIN to 50

Ω with an

insertion loss of less than 2 dB over a 5 MHz bandwidth. For the

output network, the 50

Ω load is made to present 200 Ω to the

AD8367 output. Table II provides the component values required

for 50

Ω matching at several frequencies of interest.

In situations where added loss and noise can be tolerated, a

resistive pad can be used to provide broad-band near-matched

impedances at the device terminals and the terminations.

Minimum-loss L-pad networks are used on the evaluation board

(see Figure 19) to allow easy interfacing to standard 50

Ω test

equipment. Each pad introduces an 11.5 dB power loss

(5.5 dB voltage loss).

AD8367 Scheda tecnica(PDF) 11 Page - Analog Devices

AD8367 Scheda tecnica(HTML) 11 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Scheda tecnica Scarica

Link URL