120
INPUT POWER = –30 dBm
in a single package, such as the SOT‑143 HSMS‑2865 as
shown in Figure 29.
In high power differential detectors, RF coupling from
the detector diode to the reference diode produces a
rectified voltage in the latter, resulting in errors.
Isolation between the two diodes can be obtained
by using the HSMS‑286K diode with leads 2 and 5
grounded. The difference between this product and the
conventional HSMS‑2865 can be seen in Figure 29.
OUTPUT VOLTAGE (mV)
100
3.0 µA
80
1.0 µA
10 µA
60
40
-55
0.5 µA
-35
-15
5
25
45
65
85
TEMPERATURE (
°
C)
3
4
6
5
4
Figure 25. Output Voltage vs. Temperature and Bias Current
in the 915 MHz Voltage Doubler using the HSMS-286C.
35
3.0 µA
INPUT POWER = – 30 dBm
1
HSMS-2865
SOT-143
2
1
2
3
OUTPUT VOLTAGE (mV)
25
10 µA
1.0 µA
HSMS-286K
SOT-363
Figure 29. Comparing Two Diodes.
15
0.5 µA
5
-55
The HSMS‑286K, with leads 2 and 5 grounded, offers
some isolation from RF coupling between the diodes.
This product is used in a differential detector as shown
in Figure 30.
5
25
45
65
85
PA
detector V
s
diode
-35
-15
TEMPERATURE (
°
C)
Figure 26. Output Voltage vs. Temperature and Bias Current
in the 5.80 GHz Voltage Detector using the HSMS-286B Schottky.
to differential
amplifier
HSMS-286K
Six Lead Circuits
The differential detector is often used to provide temper‑
ature compensation for a Schottky detector, as shown in
Figures 27 and 28.
bias
reference diode
Figure 30. High Isolation Differential Detector.
In order to achieve the maximum isolation, the designer
must take care to minimize the distance from leads 2
and 5 and their respective ground via holes.
Tests were run on the HSMS‑282K and the conventional
HSMS‑2825 pair, which compare with each other in the
same way as the HSMS‑2865 and HSMS‑286K, with the
results shown in Figure 31.
5000
Frequency = 900 MHz
RF diode
V
out
Square law
response
matching
network
differential
amplifier
OUTPUT VOLTAGE (mV)
Figure 27. Differential Detector.
PA
detector V
s
diode
1000
100
to differential
amplifier
HSMS-2865
10
37 dB
1
0.5
-35
HSMS-2825
ref. diode
HSMS-282K
ref. diode
reference diode
47 dB
-25
-15
-5
5
15
INPUT POWER (dBm)
Figure 28. Conventional Differential Detector.
These circuits depend upon the use of two diodes
having matched V
f
characteristics over all operating
temperatures. This is best achieved by using two diodes
11
Figure 31. Comparing HSMS-282K with HSMS-2825.
AVAGO [ AVAGO TECHNOLOGIES LIMITED ]
