![]() Small inaccuracies in the MSB resistors can entirely overwhelm the contribution of the LSB resistors. The R–2R ladder operates as a string of current dividers, whose output accuracy is solely dependent on how well each resistor is matched to the others. It is fast and has fixed output impedance R. The R–2R ladder is inexpensive and relatively easy to manufacture, since only two resistor values are required (or even one, if R is made by placing a pair of 2R in parallel, or if 2R is made by placing a pair of R in series). The main disadvantage is that this architecture requires 2 n Analog-to-digital conversion Įach tap of the string generates a different voltage, which can be compared with another voltage: this is the basic principle of a flash ADC (analog-to-digital converter). A Kelvin divider or string DAC is a string of equal valued resistors. The resistors act as voltage dividers between the referenced voltages. Resistor string network Ī string of many resistors connected between two reference voltages is called a "resistor string". ![]() The paper gives an advantage of R–2R that impedances seen by the sources are more equal.Īnother historic description is in US Patent 3108266, filed in 1955, "Signal Conversion Apparatus". A resistor ladder is an electrical circuit made from repeating units of resistors, in specific configurations.Īn R–2R ladder configuration is a simple and inexpensive way to perform digital-to-analog conversion (DAC), using repetitive arrangements of precise resistor networks in a ladder-like configuration.Ī 1953 paper "Coding by Feedback Methods" describes "decoding networks" that convert numbers (in any base) represented by voltage sources or current sources connected to resistor networks in a "shunt resistor decoding network" (which in base 2 corresponds to the binary-weighted configuration) or in a "ladder resistor decoding network" (which in base 2 corresponds to R–2R configuration) into a single voltage output.
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