APN1001 데이터 시트보기 (PDF) - Skyworks Solutions

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APN1001

Circuit Models for Plastic Packaged Microwave Diodes

Skyworks Solutions 

APPLICATION NOTE • APN1001: CIRCUIT MODELS FOR PLASTIC PACKAGED MICROWAVE DIODES

The single wire SOT-23 diode with 1.5 nH inductance will per-

form with 10.1 dB isolation at 900 MHz as a shunt connected

switch. The inductance is reduced to 1.2 nH if a parallel bond

wire is attached to the diode contact. This will increase the isola-

tion to 11.6 dB. A further reduction of inductance may be

obtained by adding a second diode chip in a common cathode

configuration. This reduces the inductance to 0.84 nH resulting in

an increase in isolation to 14.6 dB.

Since two junctions are employed, in the common cathode alter-

native, the capacitance is doubled under reverse bias. The

consequence may be an adverse effect on insertion loss. The

inductance of the dual bond wire design is similar to the common

cathode design resulting in similar performance. But, if the

package is inserted in the microstrip circuit with a gap in the

Input

Output

Gap

transmission line as shown in Figure 7, then the effective induc-

tance is reduced to below 0.4 nH and the isolation is increased to

20 dB at 900 MHz. Figure 7 shows a plot of the measured isola-

tion of the dual bond wire package versus frequency to 4 GHz. A

plot of an inductance of 1.5 nH is shown as a reference.

Table 1 shows a summary of the effective package inductance

values for the SOD-323 and SOT-23 packaged diodes with alter-

native wiring configurations using the measurement techniques

described.

0

1.5 nH

-10

w/o Gap (0.83 nH)

-20

w/Gap (0.32 nH)

-30

-40

Ground

-50

0

2

4

Frequency (GHz)

Figure 7. SOT-23 Dual Bond Wire With and Without a Gap

Package

SOT-23

SOT-23

SOT-23

SOT-23

SOT-23

SOT-323

Configuration

Single junction

Dual no gap

Dual gap

Parallel bonds

Common cathode

Single junction

S-Parameter Model

(nH @ 1 GHz)

1.45

1.2

0.5

S-Parameter Validation

(nH @ 1 GHz)

1.5

0.9

0.4

1.1

1.19

Table 1. Summary of Package Inductance Values

HP 4291A Inductance

(nH)

1.5/1.7

1.2

0.84

1.2

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

200311 Rev. A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 21, 2005

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