AD8264:  235 MHz, DC Coupled VGA and Differential Quad Output Amplifier

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. Intended for a broad range of applications, dc coupling combined with wide band-width 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 low-distortion 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 −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.

The gain range of the VGA section is 24 dB. 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 photo-multiplier tubes (PMT). Delay-free processing of wide-band video signals is also possible. The differential output amplifier permits convenient level shifting and interfacing to single-supply 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.

Applications

• Multi-Channel Data Acquisition
• Positron Emission Tomography
• Gain Trim
• Industrial and Medical Ultrasound
• Radar Receivers