GENERAL DESCRIPTION

The AD8021 is an exceptionally high performance, high speed voltage feedback amplifier that can be used in 16-bit resolution systems. It is designed to have both low voltage and low current noise (2.1 nV/√Hz typical and 2.1 pA/√Hz typical) while operating at the lowest quiescent supply current (7 mA @  ±5 V) among today’s high speed, low noise op amps. The AD8021 operates over a wide range of supply voltages from ±2.25 V to ±12 V, as well as from single 5 V supplies, making it ideal for high speed, low power instruments. An output disable pin allows further reduction of the quiescent supply current to 1.3 mA.The AD8021 allows the user to choose the gain bandwidth product that best suits the application. With a single capacitor, the user can compensate the AD8021 for the desired gain with little trade-off in bandwidth. The AD8021 is a well-behaved amplifier that settles to 0.01% in 23 ns for a 1 V step. It has a fast overload recovery of 50 ns. The AD8021 is stable over temperature with low input offset voltage drift and input bias current drift, 0.5 μV/°C and 10 nA/°C, respectively. The AD8021 is also capable of driving a 75 Ω line with ±3 V video signals. The AD8021 is both technically superior and priced considerably less than comparable amps drawing much higher quiescent current. The AD8021 is a high speed, general-purpose amplifier, ideal for a wide variety of gain configurations and can be used throughout a signal processing chain and in control loops. The AD8021 is available in both standard 8-lead SOIC and MSOP packages in the industrial temperature range of −40°C to +85°C.

 

FEATURES

Low noise

2.1 nV/√Hz input voltage noise

2.1 pA/√Hz input current noise

Custom compensation

Constant bandwidth from G = −1 to G = −10

High speed

200 MHz (G = −1)

190 MHz (G = −10)

Low power

34 mW or 6.7 mA typical for 5 V supply

Output disable feature, 1.3 mA

Low distortion

−93 dBc second harmonic, fC = 1 MHz

−108 dBc third harmonic, fC = 1 MHz

DC precision

1 mV maximum input offset voltage

0.5 μV/°C input offset voltage drift

Wide supply range, 5 V to 24 V

Low price

Small packaging

Available in SOIC-8 and MSOP-8

 

APPLICATIONS

ADC preamps and drivers

Instrumentation preamps

Active filters

Portable instrumentation

Line receivers

Precision instruments

Ultrasound signal processing

High gain circuits

 

APPLICATIONS

The typical voltage feedback op amp is frequency stabilized with a fixed internal capacitor, CINTERNAL, using dominant pole compensation. To a first-order approximation, voltage feedback op amps have a fixed gain bandwidth product. For example, if its −3 dB bandwidth is 200 MHz for a gain of G = +1; at a gain of G = +10, its bandwidth is only about 20 MHz. The AD8021 is a voltage feedback op amp with a minimal CINTERNAL of about 1.5 pF. By adding an external compensation capacitor, CC, the user can circumvent the fixed gain bandwidth limitation of other voltage feedback op amps. Unlike the typical op amp with fixed compensation, the AD8021 allows the user to:

Maximize the amplifier bandwidth for closed-loop gains between 1 and 10, avoiding the usual loss of bandwidth and slew rate.

Optimize the trade-off between bandwidth and phase margin for a particular application.

Match bandwidth in gain blocks with different noise gains, such as when designing differential amplifiers.

 

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.