AD602*

Features:

Two Channels with Independent Gain Control
        "Linear in dB" Gain Response
Two Gain Ranges:
        AD600: 0 dB to +40 dB
        AD602: 10 dB to +30 dB
Accurate Absolute Gain: 60.3 dB
Low Distortion: 60 dBc THD at 61 V Output
High Bandwidth: DC to 35 MHz (3 dB)
Stable Group Delay: 62 ns
Low Power: 125 mW (max) per Amplifier
Signal Gating Function for Each Amplifier
Drives High Speed A/D Converters
MIL-STD-883 Compliant and DESC Versions Available


Application

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


Pinout




Specifications

Supply Voltage ±VS  . . . . . . . . . . . . . . . . . . . . . . .. . . . ±7.5 V
Input Voltages
Pins 1, 8, 9, 16  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±VS
Pins 2, 3, 6, 7  . . . . . . . . . . . . . . . . . . . . . . . ±2 V Continuous
                        . . . . . . . . . . . . . . . . . . . . . . . . . ±VS for 10 ms
Pins 4, 5  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±VS
Internal Power Dissipation2
                                           . . . . . . . . . . . . . . . . . . . .600 mW
Operating Temperature Range (J)  . . . . . . . . . .0°C to +70°C
Operating Temperature Range (A)  . . . . . . . 40°C to +85°C
Operating Temperature Range (S)  . . . . . . 55°C to +125°C
Storage Temperature Range  . . . . . . . . . . .65°C to +150°C
Lead Temperature Range (Soldering 60 sec)  . . . . . .+300°C


Description

The AD600 and AD602 dual channel, low noise variable gain amplifiers are optimized for use in ultrasound imaging systems, but are applicable to any application requiring very precise gain, low noise and distortion, and wide bandwidth. Each independent channel provides a gain of 0 dB to +40 dB in the AD600 and 10 dB to +30 dB in the AD602. The lower gain of the AD602 results in an improved signal-to-noise ratio at the output. However, both products have the same 1.4 nV/Hz input noise spectral density. The decibel gain is directly proportional to the control voltage, is accurately calibrated, and is supply- and temperature-stable.

To achieve the difficult performance objectives, a proprietary circuit form-the X-AMP®-has been developed. Each channel of the X-AMP comprises a variable attenuator of 0 dB to 42.14 dB followed by a high speed fixed gain amplifier. In this way, the amplifier never has to cope with large inputs, and can benefit from the use of negative feedback to precisely define the gain and dynamics. The attenuator is realized as a seven-stage R-2R ladder network having an input resistance of 100 Ω, laser-trimmed to ±2%. The attenuation between tap points is 6.02 dB; the gain-control circuit provides continuous interpolation between these taps. The resulting control function is linear in dB.

The gain-control interfaces are fully differential, providing an input resistance of ~15 MΩ and a scale factor of 32 dB/V (that is, 31.25 mV/dB) defined by an internal voltage reference. The response time of this interface is less than 1 µs. Each channel also has an independent gating facility that optionally blocks signal transmission and sets the dc output level to within a few millivolts of the output ground. The gating control input is TTL and CMOS compatible.