Chapter 8 —
1
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2
" Microphone Preamplifier Type 2669
Phase Response
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
8
−
8
8.4 Phase Response
8.5 Effect of Temperature
As the temperature increases, the bias current in the the input amplifier increases.
This causes the inherent noise to increase and the input impedance to decrease
resulting in the effect shown in Fig.8.9.
Note:
The preamplifier can withstand temperatures up to 150°C. However, we do
not recommend that it is exposed to this temperature over a longer period of time
as the product’s life expectancy is drastically reduced. In addition, we recommend
that you don’t use high supply voltages with long cables at this temperature for the
same reason.
Fig.8.8 Phase response as a function of input (transducer) ca-
pacitance (measured with the 3m cable normally sup-
plied with the preamplifier)
Fig.8.9 Effect of temperature on inherent noise
100 1 k
– 6.0
10
4.0
Degrees
2.0
0
– 2.0
– 4.0
100 k10 k 200 k
940771e
Frequency (Hz)
6.0
20 pF
50 pF
6 pF
200 1k 10k 200k
3
10
100
nV/√Hz
940957e
30
300
25°C
50°C
150°C
100°C
100k
Frequency (Hz)
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