
S
Functional Schematic 
V 1.00 
Features 
1.    For best results at 2.4 GHz, use 8 pF 0402 profile SMT capaci-
tors on RF ports and 100 pF bypassing on pins 4 and 6.
Description 
Low Insertion Loss, 0.7 dB @ 2.4 GHz
1
High Isolation, 25 dB @ 2.4 GHz
1
Low Power Consumption, < 10 μA @ +3 V 
Low Cost Plastic SOT-363 Package 
The SW-438 is a GaAs MMIC SPDT switch in a low cost 
SOT-363 surface mount plastic package.  Typical applica-
tions include transmit/receive switching for Bluetooth and 
WLAN equipment.  The SW-438 can also be used in applica-
tions up to 500 mW in systems such as cellular, PCS, 
DCS1800, GSM, CDMA and other analog and digital wire-
less communications systems.   
M/A-COM fabricates the SW-438 using a 0.5 micron gate 
length GaAs p-HEMT process.  The process features full pas-
sivation for increased performance and reliability.
GaAs SPDT Switch 
DC– 3.0 GHz 
 RF1               GND              RF2
 V1   
  RFC
   V2
PIN 1
C
3
39pF
C
3
39pF
C
3
39pF
C=100pF
C=100pF
Broad Band Applications
 RF1               GND              RF2
 V1   
  RFC
   V2
PIN 1
C=8pF
C=8pF
C=8pF
C=100pF
C=100pF
2.4 GHz Application
External Component Requirements 
Please note the values of the external capacitors.  The ca-
pacitors at each of the RF ports are used as for achieving 
optimum insertion loss. They also provide DC blocking for 
positive control.  The 8 pF (0402) capacitor is recom-
mended
for 2 - 3 GHz operation.  If this value is changed or 
the capacitor placed too far from the
switch, the
perform-
ance will be affected.  We also recommend 100 pF bypass 
capacitors on pins 4 and 6. 
For broadband applications with positive control voltages, 
use DC blocking capacitors with value of 39 pF or more
. 
Pin Configuration 
Pin No. 
Function 
Description 
1 
RF1 
RF Input/Output 
2 
GND 
RF Ground 
3 
RF2 
RF Input/Output 
4 
V2 
Control 2 Input 
5 
RFC 
RF Common Port 
6 
V1 
Control 1 Input 
Ordering Information
Part Number
Package
SW-438TR-3000 
SW-438 on 13 Inch, 3000 piece Reel 
SW-438SMB 
SW-438 sample test board 
Mode 
(Control)
V1 
V2 
RFC-RF1 
RFC-RF2 
Positive
1
0 + 0.2V 
+2.3 to +5V 
+2.3 to +5V 
0 + 0.2V 
Off 
On 
On 
Off 
Negative 
2
0 + 0.2V 
-2.3 to +5V 
-2.3 to +5V 
0 + 0.2V 
On 
Off 
Off 
On 
Truth Table
1.
2.
External DC blocking capacitors are required on all RF ports. 
If negative control is used, DC blocking capacitors are not required on RF ports.