10

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OPAx363

OPAx364

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 0.1

μF

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 20

μs; 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 (> 1

μF). 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 10

Ω 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

10k

Figure 23. Improving Capacitive Load Drive

10

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Product Folder Links: OPA363 OPA2363 OPA364 OPA2364 OPA4364