Ultra-Low-Noise Amplifier Features Selectable Gain And Broad Bandwidth

The combination of selectable gain and low noise enables the amplifier to detect and resolve low-level input signals. Active impedance matching reduces signal reflection by matching signal-source and amplifier-input impedances without compromising input-noise performance. By using the pin-strapping options, designers can select four gains: G = 4, 8, 12 and 16. At a gain of four, the amplifier’s 200-MHz bandwidth is nearly three times that of competing devices, while a 0.85-nV/rtHz input referred voltage noise figure offers best-in-class noise performance.

ADI designed the AD8432 for communications-infrastructure and medical-ultrasound applications that require up to 200 MHz of bandwidth combined with a high channel count and variable gains. The common die and symmetrical design ensure precise phase matching between channels.

A single-ended-input amplifier, the AD8432 operates on a single 5-V supply and provides a differential output optimized to drive ADI’s AD8333 and AD8339 I/Q demodulators and phase shifters in medical ultrasound CW Doppler applications as well as a wide range of ADCs (analog-to-digital converters), such as ADI’s AD7679 18-bit, 570 kSPS PulSAR® converter and AD7952 14-bit, 1 MSPS PulSAR converter.

The AD8432 packaging features an exposed paddle that provides a low thermal-resistance path to the PCB (printed circuit board), which enables more efficient heat transfer and increases reliability.