U4314B Datasheet, PDF (5/7 Pages) TEMIC Semiconductors – Logarithmic AM Demodulator/RSSI

TELEFUNKEN Semiconductors
U4314B
120
+85°C
100
+25°C
80
60
–40°C
40
20
0
10 30
50
70
90 110
95 10462
m IF–Input Level ( dB V )
Figure 10. AM-demodulator characteristic (f_in = 10.7 MHz)
70
60
50
40
30
20
10
0
0
95 10335
20
40
60
80 100
m IF–Input Level ( dB V )
Figure 11. IAM_out of U4314B in the application circuit of
figure 12 (f_in = 107 MHz)
The following circuit is a mere proposal, how to improve
sensitivity and extend the dynamic range of U4314B to
more than 90 dB. However in most applications the basic
dynamic range of more than 60 dB is sufficient. TEMIC
TELEFUNKEN microelectronic GmbH makes no repre-
sentation that the use of this circuit will not refringe on
existing or future patents and no responsibility for the use
of the information contained herein is assumed. This
circuit is neither optimized concerning tolerances of the
components nor tested versus temperature. It should work
with a single supply voltage of 3 to 12 V. A npn transistor
array CA3045 or similar is used. At least four transistors
are needed to realize two current mirrors and the fifth acts
as a preamplifier. The variable resistor P₁ is used to com-
pensate the quiescent current of the logarithmic
demodulator output and may be replaced by a fixed resis-
W tor (typ. 3.3 k ). The total supply current depends on the
IF-input level and varies between 2 and 7 mA. It is mainly
determined by the current through the PIN diode. We
recommend to use the BA679S PIN diode available from
TEMIC TELEFUNKEN microelectronic GmbH. The
input impedance of this application circuit is approxi-
W mately 1.5 k || 13 pF.
Rev. A1: 26.06.1995
5 (7)