Digitally Programmable Variable Gain Amplifier and Driver is First to Drive Low Impedances from a Single Supply

The AD8260 VGA operates at -3dB bandwidth of 200-MHz and includes a 30-dB gain range digitally adjustable in 3-dB gain steps providing the headroom needed for losses introduced in various cabling systems. The new VGA features 2.4nV/rtHz input voltage noise and driver with a built-in gain of 1.5, which is ideal for converting DAC (digital-to-analog converter) differential output signals to a voltage that can directly drive very low impedances. The AD8260 can fully drive a 10 纹 load with 2 Vpp at 10 MHz. In addition, the chip dissipates just 93 mW of power, which is less than half that of competing devices.

The AD8260 includes a high-current driver, usable as a transmitter, and a low-noise digitally programmable VGA, which is useable as a receiver, combined in a 5 mm x 5 mm chip-scale package. The receiver section consists of a single-ended input preamplifier and linear-in-dB, differential-output VGA. The differential output facilitates the interface to modern low-voltage, high-speed ADCs (analogue-to-digital converters). Versatile single- and dual-supply operation allow gain control of negative-going pulses, such as generated by photodiodes or photo-multiplier tubes, and allows for the processing of band-pass signals on a single supply. The AD8260 preamplifier is user-configurable with external resistors for gains greater than 6 dB.

The driver is set-up to be driven by modern current output DACs, like the high-speed AD9742 12 bit, 3.3 V supply DAC.