Datasheet

APPLICATION INFORMATION
PROTECTING INPUTS FROM
OPERATING VOLTAGE
5kW
OPA369
10mAmax
V
S
V
IN
V
OUT
I
OVERLOAD
Current-limitingresistor
requiredifinputvoltage
exceedssupplyrailsby
³ 0.5V.
INPUT COMMON-MODE VOLTAGE RANGE
OPA369
OPA2369
www.ti.com ............................................................................................................................................ SBOS414B – AUGUST 2007 – REVISED DECEMBER 2008
The OPA369 family of operational amplifiers The input common-mode voltage range of the
minimizes power consumption and operates on OPA369 family typically extends to each supply rail.
supply voltages as low as 1.8V. Power-supply CMRR is specified from the negative rail to the
rejection ratio (PSRR), common-mode rejection ratio positive rail. See Figure 4 , Normalized Offset Voltage
(CMRR), and open-loop gain (A
OL
) typical values are vs Common-Mode Voltage.
in the range of 100dB or better.
When designing for ultralow power, choose system
OVER-VOLTAGE
components carefully. To minimize current
consumption, select large-value resistors. Any
Input currents are typically 10pA. However, large
resistors will react with stray capacitance in the circuit
inputs (greater than 500mV beyond the supply rails)
and the input capacitance of the operational amplifier.
can cause excessive current to flow in or out of the
These parasitic RC combinations can affect the
input pins. Therefore, in addition to keeping the input
stability of the overall system. A feedback capacitor
voltage between the supply rails, it is also important
may be required to assure stability and limit
to limit the input current to less than 10mA. This
overshoot or gain peaking.
limiting is easily accomplished with an input resistor,
as shown in Figure 24 .
Good layout practice mandates the use of a 0.1 µ F
bypass capacitor placed closely across the supply
pins.
OPA369 series op amps are fully specified and tested
from +1.8V to +5.5V ( ± 0.9V to ± 2.75V). Parameters
that vary significantly with supply voltage are shown
in the Typical Characteristic curves.
Figure 24. Input Current Protection for Voltages
The OPA369 family is designed to eliminate the input
Exceeding the Supply Voltage
offset transition region typically present in most
rail-to-rail complementary stage operational
amplifiers, which allows the OPA369 family of
amplifiers to provide superior common-mode
performance over the entire input range.
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Product Folder Link(s): OPA369 OPA2369