www.Agilent-Tech.comProductsServices & Supportwww.HP.com
Agilent-Technologies LogoSemiconductor Products
Search
Assistance
SPG home
 HPRFhelp home
 Products
  PIN Diodes
 Function
  Switch

 Select by Apps
  Attenuator
  Limiter
  Switch
 Select by Spec
 Cross Ref.  [PDF]

 What's New
 How to Buy
 
PIN Diode Application Selection Guide
SMT RF Switching Diodes

switch

Alternatives:

1. Integrated Circuit Switches

Features:

Low resistance at low current: low loss in switch
Low capacitance: fast switch

Key Parameters:

Insertion Loss:
tenths of dBs
for series configuration, need low R
for shunt configuration, need low C

Isolation:
20+ dB for single diode, 30+ for diode pair
for series configuration, need low C
for shunt configuration, need low R

Switching speed (reverse recovery time):
HSMP-389x: 100 nsec
HSMP-382x: 7 nsec
HSMP-386x: unspecified
HSMP-388x: 550 nsec

Power handling capability:
HSMP-389x: 0.5 Watt
HSMP-382x: 1 Watt
HSMP-386x: 0.5 Watt
HSMP-388x: >5 Watts

f DR (Dielectric relaxation frequency):
HSMP-389x: >3 GHz
HSMP-382x: >3 GHz
HSMP-386x: 500 MHz
HSMP-388x: 100 MHz

Markets:

TV satellite receivers (DBS, TVRO)
Cellular, PCS
ISM (Industrial-Scientific-Medical unlicensed band use)

 

Switch Diode Terms

Dielectric relaxation frequency (f DR)

What:
the frequency above which the capacitance of a PIN diode becomes independent of bias voltage.
fDR = 1 / (2 pi rho epsilon)
      where rho is the I layer bulk resistivity
      and epsilon = 1 E -12 F/cm
for a typical epi diode, rho =10 and f DR = 16 GHz [switch diode]
for a typical bulk diode, rho =2000 and f DR = 80 MHz [attenuator or switch diode]

Goodness:
A lower dielectric relaxation frequency means a wider range over which the diode will achieve minimum capacitance without external bias. In general, a low dielectric relaxation frequency is a desirable property for a diode intended to be used as a switch in a battery operated application.

Insertion Loss (I.L.)

What:
the loss of signal attributed to the diode when a switch is on (transmission state).
for a series diode switch, insertion loss can be calculated from:
I.L. = 20 log (1 + R/100)
(low resistance is needed)
for a shunt diode switch, insertion loss can be calculated from:
I.L. = 10 log [ 1 + (50 pi f C)2]
(low capacitance is needed, particularly at high frequencies)

Goodness:
less is better.

Isolation

What:
the measure of RF leakage between input and output when a switch is off.
for a series diode switch, insertion loss can be calculated from:
I.L. = 10 log [1 + 1/(200 pi f C)2]
(low resistance is needed for high isolation)
for a shunt diode switch, insertion loss can be calculated from:
I.L. = 20 log ( 1 + 25/R)
(low capacitance is needed for high isolation, particularly at high frequencies)

Goodness:
higher is better.

Power Handling Capability

What:
The RF power (Continuous Wave or pulsed) that can be handled safely by a diode switch. This number is limited by two factors: breakdown voltage and thermal resistance. Other factors that may influence power handling capability include ambient temperature, frequency, attenuation level, and pulse characteristics.

Goodness:
high power handling capability is better.

Switching Speed (also called Reverse Recovery Time)

What:
Reverse recovery time measures the time to switch the diode from ON to OFF. It depends on both the forward and reverse bias applied. With forward bias current, charge is stored in the I layer of the PIN diode. When a reverse pulse is applied, reverse current will flow for a brief period of time, known as the delay time, td. When a sufficient number of carriers have been removed, current begins to decrease. The time required for the reverse current to decrease form 90% to 10% is called the transition time, TT. The sum, td + TT, is the reverse recovery time.

Goodness:
low reverse recovery time is better.

Privacy Statement Terms of Use

this page last updated: 1 October 1999