OPA364IDBVRG4 Datasheet, PDF (10/38 Pages) Texas Instruments – 1.8V, 7MHz, 90dB CMRR, Single-Supply, Rail-to-Rail I/O Operational Amplifier

OPA363, OPA2363
OPA364, OPA2364, OPA4364
SBOS259C – SEPTEMBER 2002 – REVISED MAY 2013
www.ti.com
OPERATING VOLTAGE
The OPA363 and OPA364 series op amp parameters are fully specified from +1.8V to +5.5V. Single 0.1μF
bypass capacitors should be placed across supply pins and as close to the part as possible. Supply voltages
higher than 5.5V (absolute maximum) may cause permanent damage to the amplifier. Many specifications apply
from –40°C to +125°C. Parameters that vary significantly with operating voltages or temperature are shown in
the Typical Characteristics.
ENABLE FUNCTION
The shutdown (enable) function of the OPA363 is referenced to the negative supply voltage of the operational
amplifier. A logic level HIGH enables the op amp. A valid logic HIGH is defined as voltage greater than 75% of
the positive supply applied to the enable pin. The valid logic HIGH signal can be as much as 5.5V above the
negative supply, independent of the positive supply voltage. A valid logic LOW is defined as less than 0.8V
above the negative supply pin. If dual or split power supplies are used, care should be taken to ensure logic input
signals are properly referred to the negative supply voltage. This pin should be connected to a valid high or low
voltage or driven, not left open circuit.
The logic input is a high-impedance CMOS input. Dual op amps are provided separate logic inputs. For battery-
operated applications, this feature may be used to greatly reduce the average current and extend battery life.
The enable time is 20μs; disable time is 1μs. When disabled, the output assumes a high-impedance state. This
allows the OPA363 to be operated as a “gated” amplifier, or to have its output multiplexed onto a common
analog output bus.
CAPACITIVE LOAD
The OPA363 and OPA364 series op amps can drive a wide range of capacitive loads. However, all op amps
under certain conditions may become unstable. Op amp configuration, gain, and load value are just a few of the
factors to consider when determining stability. An op amp in unity-gain configuration is the most susceptible to
the effects of capacitive load. The capacitive load reacts with the output resistance of the op amp to create a
pole in the small-signal response, which degrades the phase margin.
In unity gain, the OPA363 and OPA364 series op amps perform well with a pure capacitive load up to
approximately 1000pF. The ESR (Equivalent Series Resistance) of the loading capacitor may be sufficient to
allow the OPA363 and OPA364 to directly drive very large capacitive loads (> 1μF). Increasing gain enhances
the amplifier’s ability to drive more capacitance; see Figure 13.
One method of improving capacitive load drive in the unity-gain configuration is to insert a 10Ω to 20Ω resistor in
series with the output, as shown in Figure 23. This significantly reduces ringing with large capacitive loads.
However, if there is a resistive load in parallel with the capacitive load, it creates a voltage divider introducing a
dc error at the output and slightly reduces output swing. This error may be insignificant. For instance, with R_L =
10kΩ and R_S = 20Ω, there is only about a 0.2% error at the output.
V+
OPAx363
OPAx364
V_IN
R_S
10W to
20W
R_L
V_OUT
C_L
Figure 23. Improving Capacitive Load Drive
10
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