AD8264

The AD8264 is a 4-channel, linear-in-dB, general-purpose variable gain amplifier (VGA)with a preamplifier (preamp), and a flexible differential output buffer. The gain range of the VGA section is 24 dB. The -3 dB bandwidth of the preamp/VGA is dc to 235 MHz, and the bandwidth of the differential driver is 80 MHz. The floating gain control interface provides a precise linear-in-dB scale of 20 dB/V and is easy to interface to a variety of external circuits. The gain of each channel is adjusted independently, and all channels are referenced to a single pin, GNLO. Combined with a multi-output, digital-to-analog converter (DAC), each section of the AD8264 can be used for active calibration or as a trim amplifier. Operation from a dual polarity power supply enables amplification of negative voltage pulses that are generated by current-sinking pulses into a grounded load, such as is typical of photodiodes or photomultiplier tubes (PMT). Delay-free processing of wide-band video signals is also possible. The differential output amplifier permits convenient level shifting and interfacing to singlesupply ADCs using the VOCM and OFSx pins. The AD8264 is available in a 40-lead, 6 mm * 6 mm LFCSP with an operating temperature range of -40°C to +105°C. Intended for a broad range of applications, dc coupling combined with wide bandwidth makes this amplifier a very good pulse processor. Each channel includes a single-ended input preamp/VGA section to preserve the wide bandwidth and fast slew rate for lowdistortion pulse applications. A 6 dB differential output buffer with common-mode and offset adjustments enable direct coupling to most modern high speed analog-to-digital converters (ADCs), using the converter reference output for perfect dc matching levels.

The features of AD8264 can be summarized as (1)low noise voltage noise: 2.3 nV/Hz/ Current noise: 2 pA/Hz; (2)wide bandwidth; (3)small signal: 235 MHz (VGAx); 80 MHz (differential output amplifier)/ Large signal: 80 MHz (1 V p-p); (4)gain range 0 to 24 dB (input to VGA output)/ 6 to 30 dB (input to differential output); (5)gain scaling: 20 dB/V; (6)DC-coupled; (7)single-ended input and differential output; (8)supplies: ±2.5 V to ±5 V; (9)low power: 140 mW per channel @ ±3.3 V.

The absolute maximum ratings of AD8264 are (1)supply voltage (VPOS, VNEG): ±6 V; (2)input voltage (INPx): VPOS, VNEG; (3)gain voltage (GNHx, GNLO): VPOS, VNEG; (4)power dissipation: 2.5 W; (5)operating temperature range: -40°C to +105°C; (6)storage temperature range: -65°C to +150°C; (7)lead temperature (soldering, 60 sec): 300°C; (8)package glass transition temperature (TG): 150°C.