AD8541/AD8542/AD8544

Rev. E | Page 12 of 20

THEORY OF OPERATION

NOTES ON THE AD854x AMPLIFIERS

The AD8541/AD8542/AD8544 amplifiers are improved

performance, general-purpose operational amplifiers.

Performance has been improved over previous amplifiers in

several ways.

Lower Supply Current for 1 MHz Gain Bandwidth

The AD854x series typically uses 45 μA of current per amplifier.

This is much less than the 200 μA to 700 μA used in earlier

generation parts with similar performance. This makes the

AD854x series a good choice for upgrading portable designs for

longer battery life. Alternatively, additional functions and

performance can be added at the same current drain.

Higher Output Current

At 5 V single supply, the short-circuit current is typically 60 μA.

Even 1 V from the supply rail, the AD854x amplifiers can

provide a 30 mA output current, sourcing or sinking.

Sourcing and sinking are strong at lower voltages, with 15 mA

available at 2.7 V and 18 mA at 3.0 V. For even higher output

currents, see the Analog Devices, Inc. AD8531/AD8532/AD8534

parts, with output currents to 250 mA. Information on these

parts is available from your Analog Devices representative, and

data sheets are available at www.analog.com.

Better Performance at Lower Voltages

The AD854x family of parts was designed to provide better ac

performance at 3.0 V and 2.7 V than previously available parts.

Typical gain-bandwidth product is close to 1 MHz at 2.7 V.

Voltage gain at 2.7 V and 3.0 V is typically 500,000. Phase

margin is typically over 60°C, making the part easy to use.