| 摘要 |
A complementary Current Tree Decoder (CTD) structure includes output drivers in the form of current sources that may be designed to pull up or down and may be clamped to provide large or small voltage transitions for driving bipolar or Field Effect Transistor (FET) second decoders. Both Up Level Decoders (ULDs) and Down Level Decoders (DLDs) may be used together to drive bipolar second decoders, thereby saving power. For similar decode functions, the device count for the complementary Current Tree Decoder (CTD) is similar to that of the True/Complement Generator (TCG) decoder, but for the same current driving capability, the CTD dissipates only one fifth of the power dissipation of the TCG decoder. The CTD uses current folding to produce the equivalent of a four tier cascode current switch (ECL). Current folding is possible through the use of both vertical PNP and NPN transistors to source and sink current in both positive and negative directions. Power dissipation is low because only one branch of the tree at a time conducts current.
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