OPA320 Datasheet, PDF (12/31 Pages) Texas Instruments – Precision, 20MHz, 0.9pA, Low-Noise, RRIO, CMOS Operational Amplifier with Shutdown

OPA320, OPA2320
OPA320S, OPA2320S
SBOS513D – AUGUST 2010 – REVISED NOVEMBER 2011
www.ti.com
APPLICATION INFORMATION
OPERATING VOLTAGE
The OPA320 series op amps are unity-gain stable
and can operate on a single-supply voltage (1.8V to
5.5V), or a split supply voltage (±0.9V to ±2.75V),
making them highly versatile and easy to use. The
power-supply pins should have local bypass ceramic
capacitors (typically 0.001μF to 0.1μF). The OPA320
amplifiers are fully specified from +1.8V to +5.5V and
over the extended temperature range of –40°C to
+125°C. Parameters that can exhibit variance with
regard to operating voltage or temperature are
presented in the Typical Characteristics.
INPUT AND ESD PROTECTION
The OPA320 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 10mA as stated in the Absolute Maximum
Ratings. Many input signals are inherently
current-limited to less than 10mA; therefore, a limiting
resistor is not required. Figure 29 shows how a series
input resistor (R_S) may be added to the driven input
to limit the input current. The added resistor
contributes thermal noise at the amplifier input and
the value should be kept to the minimum in
noise-sensitive applications.
RAIL-TO-RAIL INPUT
The OPA320 product family features true rail-to-rail
input operation, with supply voltages as low as ±0.9V
(1.8V). The design of the OPA320 amplifiers include
an internal charge-pump that powers the amplifier
input stage with an internal supply rail at
approximately 1.6V above the external supply (V_S+).
This internal supply rail allows the single differential
input pair to operate and remain very linear over a
very wide input common-mode range. A unique
zero-crossover input topology eliminates the input
offset transition region typical of many rail-to-rail,
complementary input stage operational amplifiers.
This topology allows the OPA320 to provide superior
common-mode performance (CMRR > 110dB,
typical) over the entire common-mode input range,
which extends 100mV beyond both power-supply
rails. When driving analog-to-digital converters
(ADCs), the highly linear V_CM range of the OPA320
assures maximum linearity and lowest distortion.
PHASE REVERSAL
The OPA320 op amps are designed to be immune to
phase reversal when the input pins exceed the supply
voltages, therefore providing further in-system
stability and predictability. Figure 30 shows the input
voltage exceeding the supply voltage without any
phase reversal.
4
V_S = ±2.5V
V_IN
3
2
V+
1
I_OVERLOAD
0
10mA, Max
V_IN
OPA320
V_OUT
-1
R_S
-2
V_OUT
Figure 29. Input Current Protection
-3
-4
-500
-250
0
250
500
Time (ms)
750 1000
Figure 30. No Phase Reversal
12
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