The AD8002 is a dual, low power, high speed amplifier designed for use with ±5 V supplies. The AD8002 has a unique transimpedance linearization circuit that allows the AD8002 to drive video loads with excellent differential gain with phase performance of as little as 50 mW per amplifier.

The AD8002 is a current feedback amplifier with a gain characteristic of 0.1 dB to 60 MHz flatness while providing differential gain and

Phase errors of 0.01% and 0.02° make the AD8002 ideal for professional video electronics such as cameras and video switching. In addition, the low distortion and fast settling of the AD8002 make it ideal for buffering high-speed analog-to-digital converters (ADCs).

The AD8002 consumes a maximum of 5.0 mA/amp (VS = ±5 V) and can operate on a single 12 V supply, but is capable of supplying over 70 mA of load current. Available in 8-pin SOIC and MSOP packages. These features make this amplifier suitable for portable and battery-powered applications where size and power are critical. A bandwidth of 600 MHz and a slew rate of 1 200 V/µs make the AD8002 useful in many general-purpose high-speed dual-supply operations up to ±6 V and a single supply requiring a 6 V to 12 V supply. The AD8002 is available over the industrial temperature range of -40°C to +85°C.

Pin Connection Block Diagram

feature

Excellent video specs (RL = 150Ω, G = +2)

Gain Flatness: 0.1 dB to 60 MHz

Differential Gain Error: 0.01%

Differential Phase Error: 0.02°

low power

Maximum Supply Current (50 mW): 5.0 mA/amp

High speed, fast and stable

-3 dB bandwidth (G = +1): 600 MHz

-3 dB bandwidth (G = +2): 500 MHz

Slew rate: 1200 V/μs

Settling time to 0.1%: 16 ns

low distortion

THD at fC = 5 MHz: -65 dBc

Third-order intercept at f1 = 10 MHz: 33 dBm

SFDR at f = 5 MHz: -66 dB

Crosstalk at f = 5 MHz: -60 dB

high output drive

Over 70 mA output current

Drives up to 8 rear-connected 75Ω loads (4

load/side) while maintaining a good difference

Gain/Phase Performance (0.01%/0.17°)

Available in 8-pin SOIC and MSOP packages

application

analog to digital converter

video line driver

Differential Line Driver

professional camera

video switcher

Special effect

RF receiver

PIN configuration and function description

8-pin SOIC

8-pin MSOP

test circuit

Test circuit, gain = +1

Test circuit, gain = +2

Theory of Operation

Analysis of the AD8002 can familiarize the operation with terms. The open-loop behavior of the AD8002 is expressed as transimpedance, ΔVOUT/ΔI-INx or TZ. The open-loop transimpedance behaves like an open-loop voltage gain voltage feedback amplifier, i.e. with a large DC value and a frequency drop of about 6 dB/octave. Because the value of RIN is proportional to 1/gm, the equivalent voltage gain is only TZ × gm, where gm in question is the transconductance of the input stage. This results in a low open-loop input impedance at the inverting input.

Recognizing that G×RIN << R1 is a low gain, the amplifier can see that its bandwidth is first-order independent of gain (G). Given that the extra pole causes excess phase high frequencies, going below the minimum feedback resistance can cause peaking or ringing. This fact is used to determine the optimal feedback resistance RF. In practice, the parasitic capacitance at the inverting input also increases the phase in the feedback loop; thus choosing the optimum value

RF can be hard. Achieving and maintaining gain flatness better than 0.1 dB at frequencies above 10 MHz requires careful consideration. Several issues are discussed in the following sections. Choice of feedback and gain resistors Fine-scale gain flatness varies somewhat with feedback resistance. Therefore, it is recommended to determine the optimal resistor value as soon as possible, using a 1% tolerance value if you want to maintain flatness over a wide range

production batch. In addition, resistors of different structures have different characteristics of the associated parasitic capacitances. Lead components are not recommended

AD8002.

Operation as a Video Line Driver The AD8002 is designed to provide a good performance video line driver. The important specifications of the difference are gain (0.01%) and differential phase (0.02°) to meet the most stringent HDTV requirements each driving a video load amplifier. The AD8002 can also drive four rear-end loads (two each), as shown in the figure below, with equally impressive performance (0.01%, 0.07°). Another important consideration is isolation between loads in multi-load applications. The AD8002 drives two 75Ω rear-connected loads with more than 40 dB of isolation at 5 MHz.

The AD8002 is ideal for driving high-speed analog-to-digital converters such as the AD9058. The AD9058 is a dual, 8-bit, 50 MSPS ADC. In the figure below, the AD8002 drives the input of the AD9058, configured for the 0 V to 2 V. range. The bipolar input signal is buffered, amplified (-2×) and offset (1.0 V) to the appropriate input range of the ADC. Use the AD9058's internal 2 V reference to connect to both

ADCs reduce the number of components required to create a complete data acquisition external system. A 20Ω resistor in series with the ADC input helps the ADC drive the 10 pF ADC input capacitance. The AD8002 only adds 100 mW of power dissipation rather than limiting the performance of the circuit. Using the Single-Ended-to-Differential Driver AN AD8002 The two halves of the AD8002 can be configured to create a single-ended-to-differential high-speed driver with -3 dB bandwidth in excess of 200 MHz, as shown in the figure below. While the individual op amps are current feedback op amps, the overall architecture produces circuits with the properties typically associated with voltage feedback amplifiers, but offering the inherent speed advantages of current feedback amplifiers. In addition, the gain of the circuit can be changed by changing a single resistor, RF, which is usually not possible in a dual op amp differential driver.

Differential Line Driver He 2

AD8002 drives dual ADCs