580 Pleasant St.
Watertown, MA 02472
PH: (617) 926-0404
FAX: (617) 924-1235
UM9552
Features
•
•
•
•
Low Frequency Attenuator
HF/LF Band Operation
Long Lifetime (70
µ
s typ.)
Very Low Distortion (IP3 @ 455 KHz = < 60 dBm)
PIN DIODE
ATTENUATOR
Description
The UM9552 is a very long minority carrier
lifetime (70
µ
s typical) PIN DIODE that has been
developed for low HF or LF Band Attenuator
Applications. They have been evaluated for attenuator
linearity and distortion characteristics in a Bridge Tee
Attenuator Circuit at 455 KHz (the common intermediate
frequency for AM transmitters and receivers). When the
UM9552’s are used as the two variable resistors in the
Bridged Tee Circuit, the Third Order Intermodulation
Products are below -60 dBc with 0 dBm input power
over an attenuation range of 4 dB to 30 dB.
These thicker, longer lifetime PIN diodes exhibit
a more linear forward biased resistance (R
S
) vs forward
bias current (If) relationship, which greatly simplifies the
design of the driver circuits that supply the bias
currents over the specified attenuation range. This task
is simplified if the low attenuation range is truncated
and the few dB are compensated by commercially
available, inexpensive 4 to 6 dB gain blocks.
TYPICAL POWER LEVEL vs FORWARD BIAS CURRENT
40
f1 = F +/- 1 KHz
f2 = F +/- 1 KHz
35
65
70
POWER LEVEL/TONE (dBm)
500KHz
250KHz
150KHz
25
55
20
50
TAU = 0.1 ms
15
1
2
3
4
5
6
7
8
10
If NEEDED TO OBTAIN AN IM3 OF - 60 dBc (mA)
45
Electrical Specifications (25°C)
Test
Diode Resistance R
S
Min.
Typ.
18.0
2.0
.25
15
70
60
Max.
Units
Ω
Ω
Ω
pF
µ
A
µ
s
dBm
Conditions
F = 455 KHz, I
f
= 1 mA
F = 455 KHz, I
f
=10 mA
F = 455 KHz, I
f
= 100 mA
F = 1 MHz, 100 V
V
R
= 50 V
I
f
=10 mA / 100 V
Power in = 0 dBm / Tone
F1 = 454 KHz F2 = 456 KHz
Circuit Drawing #B14433
25°C Stud Temperature
°
Capacitance C
T
Reverse Current I
R
Carrier Lifetime
τ
IP3
0.4
20
10
50
50
Thermal Resistance
1.0
°
C / W
MSCO867B 11-30-98
DSW UM9552 <B>(34943)
IP3 (dBm)
30
60
stm32/stm8
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