| 摘要 |
An integrated circuit digital to analog converter using a R/2R resistor ladder has, in a typical bit stage, a bit current transistor (eg 60-1), and a waste current transistor (eg 61-1) connected as shown, with the collector of the latter connected to a metal ground voltage conductor (41) at a "shared node" also connected to the ladder rung resistor. The waste current transistor switches waste current into the shared node, rather than into a separate waste current ground conductor. This results in substantially less voltage variation across the distributed resistance of the metal ground voltage conductor, and consequently lower non-linearity. Most- significant bits may use binary-weighted constant-current sources, rather than the ladder. <IMAGE> |
