
Switched-Capacitor Data Converters
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A 2-bit thermometer-coded current-steering DAC is shown in Figure 5.2(b). In
general, this type of DAC architecture employs 2
M
equal current sources for trans-
forming an M-bit binary input to avoid overloading. As shown, a 2-bit input binary
code is decoded into the equivalent 4-bit thermometer code, with each bit directing
the output of a current source, either to the op-amp or to ground. And the currents
sent to the inverting terminal of the op-amp are superposed and converted into an
analog voltage by the feedback resistor R
0
.
In general, the conversion accuracy of a current-steering DAC greatly depen