AD605

Features:

Bandwidth: 40 MHz (3 dB)
Differential Input
Absolute Gain Range Programmable:
14 dB to +34 dB (FBK Shorted to OUT) Through
0 dB to +48 dB (FBK Open)
Variable Gain Scaling: 20 dB/V Through 40 dB/V
Stable Gain with Temperature and Supply Variations
Single-Ended Unipolar Gain Control
Output Common-Mode Independently Set
Power Shutdown at Lower End of Gain Control
Single 5 V Supply
Low Power: 90 mW/Channel
Drives A/D Converters Directly




Application

Ultrasound and Sonar Time-Gain Control
High Performance AGC Systems
Signal Measurement




Pinout








Specifications



Supply Voltage +VS
Pins 12, 13 (with Pins 4, 5 = 0 V) . . . . . . . . . . . . . . . 6.5 V
Input Voltage Pins 13, 69, 16 . . . . . . . . . . . . . . . .VPOS, 0
Internal Power Dissipation
Plastic (N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 W
Small Outline (R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 W
Operating Temperature Range . . . . . . . . .40°C to +85°C
Storage Temperature Range . . . . . . . . . . 65°C to +150°C
Lead Temperature, Soldering 60 seconds . . . . . . . . .300°C




Description

The AD605 is a low noise, accurate, dual channel, linear-in-dB variable gain amplifier, which is optimized for any application requiring high performance, wide bandwidth variable gain control. Operating from a single 5 V supply, the AD605 provides differential inputs and unipolar gain control for ease of use. Added flexibility is achieved with a user-determined gain range and an external reference input which provides user-determined gain scaling (dB/V).

The high performance linear-in-dB response of the AD605 is achieved with the differential input, single supply, exponential amplifier (DSX-AMP) architecture. Each of the DSX-AMPs comprise a variable attenuator of 0 dB to 48.4 dB followed by a high speed fixed gain amplifier. The attenuator is based on a 7-stage R-1.5R ladder network. The attenuation between tap points is 6.908 dB, and 48.360 dB for the entire ladder network. The DSX-AMP architecture results in 1.8 nV/Hz input noise spectral density and will accept a ± 2.0 V input signal when VOCM is biased at VP/2.

Each independent channel of the AD605 provides a gain range of 48 dB which can be optimized for the application. Gain ranges between 14 dB to +34 dB and 0 dB to +48 dB can be selected by a single resistor between pins FBK and OUT. The lower and upper gain ranges are determined by shorting pin FBK to OUT, or leaving pin FBK unconnected, respectively. The two channels of the AD605 can be cascaded to provide 96 dB of very accurate gain range in a monolithic package.