Analog Devices

The AD603 is a low noise, voltage-controlled amplifier for use in RF and IF AGC systems. It provides accurate, pin-selectable gains of −11 dB to +31 dB with a bandwidth of 90 MHz or +9 dB to 51+ dB with a bandwidth of 9 MHz. Any intermediate gain range may be arranged using one external resistor. The input referred noise spectral density is only 1.3 nV/√Hz, and power consumption is 125 mW at the recommended ±5 V supplies.The decibel gain is linear in dB, accurately calibrated, and stable over temperature and supply. The gain is controlled at a high impedance (50 MΩ), low bias (200 nA) differential input; the scaling is 25 mV/dB, requiring a gain control voltage of only 1 V to span the central 40 dB of the gain range. An overrange and underrange of 1 dB is provided whatever the selected range. The gain control response time is less than 1 μs for a 40 dB change.The differential gain control interface allows the use of either differential or single-ended positive or negative control voltages. Several of these amplifiers may be cascaded and their gain control gains offset to optimize the system SNR.The AD603 can drive a load impedance as low as 100 Ω with low distortion. For a 500 Ω load in shunt with 5 pF, the total harmonic distortion for a ±1 V sinusoidal output at 10 MHz is typically −60 dBc. The peak specified output is ±2.5 V minimum into a 500 Ω load.The AD603 uses a patented proprietary circuit topology—the X-AMP®. The X-AMP comprises a variable attenuator of 0 dB to −42.14 dB followed by a fixed-gain amplifier. Because of the attenuator, the amplifier never has to cope with large inputs and can use negative feedback to define its (fixed) gain and dynamic performance. The attenuator has an input resistance of 100 Ω, laser trimmed to ±3%, and comprises a 7-stage R-2R ladder network, resulting in an attenuation between tap points of 6.021 dB. A proprietary interpolation technique provides a continuous gain control function that is linear in dB.The AD603 is specified for operation from −40°C to +85°C.ApplicationsRF/IF AGC amplifiersVideo gain controlsA/D range extensionsSignal measurements

The AD621 is an easy to use, low cost, low power, high accuracy instrumentation amplifier which is ideally suited for a wide range of applications. Its unique combination of high performance, small size and low power, outperforms discrete in amp implementations. High functionality, low gain errors and low gain drift errors are achieved by the use of internal gain setting resistors. Fixed gains of 10 and 100 can be easily set via external pin strapping. The AD621 is fully specified as a total system, therefore, simplifying the design process.For portable or remote applications, where power dissipation, size and weight are critical, the AD621 features a very low supply current of 1.3 mA max and is packaged in a compact 8-pin SOIC, 8-pin plastic DIP or 8-pin cerdip. The AD621 also excels in applications requiring high total accuracy, such as precision data acquisition systems used in weigh scales and transducer interface circuits. Low maximum error specifications including nonlinearity of 10 ppm, gain drift of 5 ppm°/C, 50 µV offset voltage and 0.6 mV/°C offset drift ("B" grade), make possible total system performance at a lower cost than has been previously achieved with discrete designs or with other monolithic instrumentation amplifiers.When operating from high source impedances, as in ECG and blood pressure monitors, the AD621 features the ideal combination of low noise and low input bias currents. Voltage noise is specified as 9 nV/(root) Hz at 1 kHz and 0.28 µV p-p from 0.1 Hz to 10 Hz. Input current noise is also extremely low at 0.1 pA/Hz. The AD621 outperforms FET input devices with an input bias current specification of 1.5 nA max over the full industrial temperature range.

The AD622 is a low cost, moderately accurate instrumentation amplifier in the traditional pin configuration that requires only one external resistor to set any gain between 2 and 1000. For a gain of 1, no external resistor is required. The AD622 is a complete difference or subtractor amplifier system that also provides superior linearity and common-mode rejection by incorporating precision laser-trimmed resistors.The AD622 replaces low cost, discrete, two or three op amp instrumentation amplifier designs and offers good common-mode rejection, superior linearity, temperature stability, reliability, power, and board area consumption. The low cost of the AD622 eliminates the need to design discrete instrumentation amplifiers to meet stringent cost targets. While providing a lower cost solution, it also provides performance and space improvements.ApplicationsTransducer interfaceLow cost thermocouple amplifierIndustrial process controlsDifference amplifierLow cost data acquisition