SLOS735
–
AUGUST 2011
shows a single-supply, electret microphone application where V
CM
is provided by a resistive divider. The
divider also provides the bias voltage for the electret element.
Clean 3.3V Supply
49kΩ
3.3V
4kΩ
OPA365
V
OUT
Electret
Microphone
6kΩ
5kΩ
1µF
Figure 3. Microphone Preamplifier
Input and ESD Protection
The OPA365 incorporates internal electrostatic discharge (ESD) protection circuits on all pins. In the case of
input and output pins, this protection primarily consists of current steering diodes connected between the input
and power-supply pins. These ESD protection diodes also provide in-circuit, input overdrive protection, provided
that the current is limited to 10 mA as stated in the Absolute Maximum Ratings.
shows how a series
input resistor may be added to the driven input to limit the input current. The added resistor contributes thermal
noise at the amplifier input and its value should be kept to the minimum in noise-sensitive applications.
V+
I
OVERLOAD
10mA max
OPA365
V
OUT
V
IN
5kΩ
Figure 4. Input Current Protection
Copyright
©
2011, Texas Instruments Incorporated
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