DESCRIPTION

The OPA334 and OPA335 series of CMOS operational amplifiers use auto-zeroing techniques to simultaneously provide very low offset voltage (5µV max), and near-zero drift over time and temperature. These miniature, high-precision, low quiescent current amplifiers offer high input impedance and rail-to-rail output swing. Single or dual supplies as low as +2.7V (±1.35V) and up to +5.5V (±2.75V) may be used. These op amps are optimized for low-voltage, single-supply operation.
The OPA334 family includes a shutdown mode. Under logic control, the amplifiers can be switched from normal operation to a standby current of 2µA. When the Enable pin is connected high, the amplifier is active. Connecting Enable low disables the amplifier, and places the output in a high impedance state.
The OPA334 (single version with shutdown) comes in MicroSIZE SOT23-6. The OPA335 (single version without shutdown) is available in SOT23-5, and SO-8. The OPA2334 (dual version with shutdown) comes in MicroSIZE MSOP-10.
The OPA2335 (dual version without shutdown) is offered in the MSOP-8 and SO-8 packages. All versions are specified for operation from –40°C to +125°C.

 

CARACTÉRISTIQUES

● LOW OFFSET VOLTAGE: 5µV (max)
● ZERO DRIFT: 0.05µV/°C (max)
● QUIESCENT CURRENT: 285µA
● SINGLE-SUPPLY OPERATION
● SINGLE AND DUAL VERSIONS
● SHUTDOWN
● MicroSIZE PACKAGES

 

CANDIDATURES

● TRANSDUCER APPLICATIONS
● TEMPERATURE MEASUREMENT
● ELECTRONIC SCALES
● MEDICAL INSTRUMENTATION
● BATTERY-POWERED INSTRUMENTS
● HANDHELD TEST EQUIPMENT

 

INFORMATIONS SUR LES APPLICATIONS

The OPA334 and OPA335 series op amps are unity-gain stable and free from unexpected output phase reversal. They use auto-zeroing techniques to provide low offset voltage and very low drift over time and temperature.
Good layout practice mandates use of a 0.1µF capacitor placed closely across the supply pins.
For lowest offset voltage and precision performance, circuit layout and mechanical conditions should be optimized. Avoid temperature gradients that create thermoelectric (Seebeck) effects in thermocouple junctions formed from connecting dissimilar conductors. These thermally-generated potentials can be made to cancel by assuring that they are equal on both input terminals.
• Use low thermoelectric-coefficient connections (avoid dissimilar metals).
• Thermally isolate components from power supplies or other heat-sources.
• Shield op amp and input circuitry from air currents, such as cooling fans.
Following these guidelines will reduce the likelihood of junctions being at different temperatures, which can cause thermoelectric voltages of 0.1µV/°C or higher, depending on materials used.

 

OPERATING VOLTAGE

The OPA334 and OPA335 series op amps operate over a power-supply range of +2.7V to +5.5V (±1.35V to ±2.75V). Supply voltages higher than 7V (absolute maximum) can permanently damage the amplifier. Parameters that vary over supply voltage or temperature are shown in the Typical Characteristics section of this data sheet.

 

OPA334 ENABLE FUNCTION

The enable/shutdown digital input is referenced to the Vsupply voltage of the amp. A logic high enables the op amp. A valid logic high is defined as > 75% of the total supply voltage.
The valid logic high signal can be up to 5.5V above the negative supply, independent of the positive supply voltage. A valid logic low is defined as < 0.8V above the V– supply pin. If dual or split power supplies are used, be sure that logic input signals are properly referred to the negative supply voltage. The Enable pin must be connected to a valid high or low voltage, or driven, not left open circuit.
The logic input is a high-impedance CMOS input, with separate logic inputs provided on the dual version. For batteryoperated applications, this feature can be used to greatly reduce the average current and extend battery life.
The enable time is 150µs, which includes one full auto-zero cycle required by the amplifier to return to VOS accuracy. Prior to this time, the amplifier functions properly, but with unspecified offset voltage.
Disable time is 1µs. When disabled, the output assumes a high-impedance state. This allows the OPA334 to be operated as a gated amplifier, or to have the output multiplexed onto a common analog output bus.