DAC_controlled_ctmplifier

Published:2009/7/25 5:34:00 Author:Jessie | From:SeekIC

Figure 9-36 shows a DAC1000 connected to control the output of an LF351 amplifier. In this circuit, the DAC is used as the feedback element for an inverting amplifier. The R-2R ladder digitally adjusts the amount of output signal fed back to the amplifier summing junction. The feedback resistance can be thought of as varying from about 15 kΩ to infinity when the input code changes from full-scale to zero. The internal feedback resistor is used as the amplifier input resistor. When the input code is all 0s, the feedback loop is opened and the op-amp output saturates. NATIONAL SEMICONDUCTOR, APPLICATION NorE 271, 1994, P. 667.



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