OPA365 Datasheet, PDF (9/24 Pages) Burr-Brown (TI) – 2.2V, 50MHz, Low-Noise, Single-Supply Rail-to-Rail OPERATIONAL AMPLIFIERS

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Figure 2 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 elec-
tret element.
INPUT AND ESD PROTECTION
The OPA365 incorporates internal electrostatic dis-
charge (ESD) protection circuits on all pins. In the case
of input and output pins, this protection primarily con-
sists of current steering diodes connected between the
input and power-supply pins. These ESD protection
diodes also provide in-circuit, input overdrive protec-
tion, provided that the current is limited to 10mA as
stated in the Absolute Maximum Ratings. Figure 3
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.
RAIL-TO-RAIL INPUT
The OPA365 product family features true rail-to-rail in-
put operation, with supply voltages as low as ±1.1V
(2.2V). A unique zer∅-crossover input topology elimi-
nates the input offset transition region typical of many
rail-to-rail, complementary stage operational amplifiers.
This topology also allows the OPA365 to provide superi-
or common-mode performance over the entire input
range, which extends 100mV beyond both power-sup-
ply rails, as shown in Figure 4. When driving ADCs, the
highly linear V_CM range of the OPA365 assures that the
op amp/ADC system linearity performance is not com-
promised.
OPA365
OPA2365
SBOS365D − JUNE 2006 − REVISED JUNE 2009
Clean 3.3V Supply
4kΩ
49kΩ
3.3V
OPA 365
Electret
6kΩ
5kΩ
Microphone
1µF
V_OUT
Figure 2. Microphone Preamplifier
I_OVERLOAD
10mA max
V_IN
5kΩ
V+
OPA 36 5
V_OUT
Figure 3. Input Current Protection
OFFSET VOLTAGE vs COMMON−MODE VOLTAGE
200
V_S = ±2.75V
150
100
OPA365
50
0
−50
−100
−150
Competitors
−200
−3
−2
−1
0
1
2
3
Common−Mode Voltage (V)
Figure 4. OPA365 has Linear Offset Over the
Entire Common-Mode Range
9