FEATURES

VERY LOW NOISE: 0.7nV/
Hz

LOW-NOISE PREAMP (LNP)

− Active Termination

− Programmable Gains: 3, 12, 18, 22dB

− Programmable Input Impedance (RF)

− Buffered, Differential Outputs for CW

Processing

− Excellent Input Signal Handling

Capabilities

LOW-NOISE VARIABLE-GAIN AMPLIFIER

− High/Low-Mode (0/+6dB)

− 52dB Gain Control Range

− Linear Control Response: 22dB/V

− Switchable Differential Inputs

− Adjustable Output Clipping-Level

BANDWIDTH: 42MHz

HARMONIC DISTORTION: −55dB

5V SINGLE SUPPLY

LOW-POWER: 154mW/Channel

POWER-DOWN MODES

APPLICATIONS

MEDICAL AND INDUSTRIAL ULTRASOUND

SYSTEMS

− Suitable for 10-Bit and 12-Bit Systems

TEST EQUIPMENT

DESCRIPTION

The VCA2615 is a dual-channel, variable gain amplifier

consisting of a Low-Noise Preamplifier (LNP) and a Variable-

Gain Amplifier (VGA). This combination along with the device

features makes it well-suited for a variety of ultrasound

systems.

The LNP offers a high level of flexibility to adapt to a wide range

of systems and probes. The LNP gain can be programmed to

one of four settings (3dB, 12dB, 18dB, 22dB), while

maintaining excellent noise and signal handling

characteristics. The input impedance of the LNP can be

controlled by selecting one of the built-in feedback resistors.

This active termination allows the user to closely match the

LNP to a given source impedance, resulting in optimized

overall system noise performance. The differential LNP

outputs are provided either as buffered outputs for further CW

processing, or fed directly into the variable-gain amplifier

(VGA). Alternatively, an external signal can be applied to the

differential VGA inputs through a programmable switch.

Following a linear-in-dB response, the gain of the VGA can be

varied over a 52dB range with a 0.2V to 2.5V control voltage

common to both channels of the VCA2615. In addition, the

overall gain can be switched between a 0dB and +6dB

postgain, allowing the user to optimize the output swing of

VCA2615 for a variety of high-speed Analog-to-Digital

Converters (ADCs). As a means to improve system overload

recovery time, the VCA2615 provides an internal clipping

function where an externally applied voltage sets the desired

clipping level.

The VCA2615 operates on a single +5V supply and is

available in a small QFN-48 (7x7mm) or TQFP package.