CN0025: Precision, AC Reference Signal Attenuator Using the AD5546/AD5556 Multiplying DAC

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OVERVIEW

Circuit Note PDF, 09/2010 (pdf, 80 kB)
Benefits & Features
  • 14-/16-bit multiplying DAC
  • AC attenuator circuit
Products Used
    Applications: 
  • Programmable Logic Controllers/ Distributed Control Systems

CIRCUIT FUNCTION AND BENEFITS

This circuit provides precision, ac signal attenuation using the AD5546/AD5556 DAC and the AD8610 precision operational amplifier. This circuit provides accurate, low noise, high speed output voltage capability and is well suited for process control, automatic test equipment, and digital calibration applications.

Figure 1: AC Signal Attenuation Configuration Using the AD5546/56 Precision DAC and the AD8610 Precision Op Amp (Simplified Schematic)

CIRCUIT DESCRIPTION

The AD5546/AD5556 are precision 16-/14-bit, multiplying, low power, current output, parallel input DACs. They operate from a single 2.7 V to 5.5 V supply with ±10 V multiplying references for 4-quadrant outputs. Multiplying bandwidth is 4 MHz. Built in 4-quadrant resistors facilitate resistance matching and temperature tracking that minimize the number of components needed for multiquadrant applications. Besides handling digital waveforms decoded from parallel input data, the AD5546/ AD5556 handle low frequency ac reference signals for signal attenuation, channel equalization, and waveform generation applications.

An op amp is used in the current-to-voltage (I-V) stage of this circuit. An op amp’s bias current and offset voltage are both important selection criteria for use with precision current output DACs. Therefore, this circuit employs the AD8610 op amp, which has ultralow offset voltage (100 μV maximum for B grade) and bias current (10 pA maximum). The value of C8 for this circuit is 2.2 pF, which is optimized to compensate for the external output capacitance of the DAC.

SAMPLE PRODUCTS USED IN THIS CIRCUIT

Product Description Available Product Models to Sample
AD5546 Current-Output Parallel-Input, 16-Bit Digital-to-Analog Converter AD5546CRUZ AD5546BRUZ
AD5556 Current-Output Parallel-Input, 14-Bit Digital-to-Analog Converter AD5556CRUZ
AD8610 Precision, Low Input Bias Current, Wide BW JFET Single Op Amp AD8610ARMZ-R7
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