HSMS282X datasheet(5/14 Pages) HP

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Applications Information

Product Selection

Agilent’s family of surface mount

Schottky diodes provide unique

solutions to many design prob-

lems. Each is optimized for

certain applications.

The first step in choosing the right

product is to select the diode type.

All of the products in the

HSMS-282x family use the same

diode chip – they differ only in

package configuration. The same

is true of the HSMS-280x, -281x,

285x, -286x and -270x families.

Each family has a different set of

characteristics, which can be

compared most easily by consult-

ing the SPICE parameters given

on each data sheet.

The HSMS-282x family has been

optimized for use in RF applica-

tions, such as

DC biased small signal

detectors to 1.5 GHz.

Biased or unbiased large

signal detectors (AGC or

power monitors) to 4 GHz.

Mixers and frequency

multipliers to 6 GHz.

The other feature of the

HSMS-282x family is its

unit-to-unit and lot-to-lot consis-

tency. The silicon chip used in this

series has been designed to use

the fewest possible processing

steps to minimize variations in

diode characteristics. Statistical

data on the consistency of this

product, in terms of SPICE

parameters, is available from

Agilent.

For those applications requiring

very high breakdown voltage, use

the HSMS-280x family of diodes.

Turn to the HSMS-281x when you

need very low flicker noise. The

HSMS-285x is a family of zero bias

detector diodes for small signal

applications. For high frequency

detector or mixer applications,

use the HSMS-286x family. The

HSMS-270x is a series of specialty

diodes for ultra high speed

clipping and clamping in digital

circuits.

Schottky Barrier Diode

Characteristics

Stripped of its package, a

Schottky barrier diode chip

consists of a metal-semiconductor

barrier formed by deposition of a

metal layer on a semiconductor.

The most common of several

different types, the passivated

diode, is shown in Figure 10,

along with its equivalent circuit.

RS is the parasitic series resis-

tance of the diode, the sum of the

bondwire and leadframe resis-

tance, the resistance of the bulk

layer of silicon, etc. RF energy

coupled into RS is lost as heat—it

does not contribute to the recti-

fied output of the diode. CJ is

parasitic junction capacitance of

the diode, controlled by the thick-

ness of the epitaxial layer and the

diameter of the Schottky contact.

Rj is the junction resistance of the

diode, a function of the total

current flowing through it.

METAL

SCHOTTKY JUNCTION

PASSIVATION

N-TYPE OR P-TYPE EPI

LAYER

N-TYPE OR P-TYPE SILICON SUBSTRATE

CROSS-SECTION OF SCHOTTKY

BARRIER DIODE CHIP

EQUIVALENT

CIRCUIT

8.33 X 10-5 nT

Rj = –––––––––––– = RV – R s

I S + Ib

0.026

≈ ––––– at 25°C

I S + Ib

where

n = ideality factor (see table of

SPICE parameters)

T = temperature in

°K

IS = saturation current (see

table of SPICE parameters)

Ib = externally applied bias

current in amps

Rv = sum of junction and series

resistance, the slope of the

V-I curve

IS is a function of diode barrier

height, and can range from

picoamps for high barrier diodes

to as much as 5

µA for very low

barrier diodes.

The Height of the Schottky

Barrier

The current-voltage characteristic

of a Schottky barrier diode at

room temperature is described by

the following equation:

V - IRS

I = IS (e

–––––

– 1)

0.026

On a semi-log plot (as shown in

the Agilent catalog) the current

graph will be a straight line with

inverse slope 2.3 X 0.026 = 0.060

volts per cycle (until the effect of

Figure 10. Schottky Diode Chip.

88759/02-5.PM6.0J

2001.04.25, 6:41 PM

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