34 / 69 page
Telit GE863-QUAD / GE863-PY
Hardware User guide
1vv0300697, Rev. ISSUE#0, - 21/11/05
Reproduction forbidden without Telit Communication written authorization – All Right reserved – Right of modification reserved
page 34 of 69
6.4.2
Buffered Unbalanced (Single Ended) Mic.
A sample schematic for a buffered unbalanced (single ended) microphone can be:
The schematic does not include the required mic. biasing circuitry. For the biasing the same
circuit as seen before can be used; to be noticed that the capacitor C3 on the unbalanced biasing
circuit is not anymore needed if this Buffered design is used.
Two different configurations are used, one inverting and the other not inverting, hence an
additional +6dB (2 times) gain is achieved by doubling the mic. signal path.
The gain of the not inverting buffer is given by the formula:
720
719
1
R
R
Gain
+
=
and hence it cannot be less than 1. In the example shown the gain of the not inverting buffer is
1,5 (4dB).
While the gain of the inverting buffer is given by the formula:
708
711
R
R
Gain
=
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
