Decoder circuitry with balanced propagation delay and minimized input

Abstract

A logic circuit implementing a logic NAND function with respect to a first input signal and a second input signal is described. First and second P-channel transistors are coupled in parallel to a power supply and an output node. Each of the first and second P-channel transistors receives the respective one of the first and second input signals. A first circuit branch has a first and a second N-channel transistor. The first N-channel transistor has a first end coupled to the output node and a second end coupled to a first end of the second N-channel transistor. The second N-channel transistor has a second end coupled to ground. The first N-channel transistor receives the first input signal and the second N-channel transistor receives the second input signal. A second circuit branch has a third and a fourth N-channel transistor. The third N-channel transistor has a first end coupled to the output node and a second end coupled to a first end of the fourth N-channel transistor. The fourth N-channel transistor has a second end coupled to ground. The third N-channel transistor receives the second input signal and the fourth N-channel transistor receives the first input signal such that the logic circuit has a balanced propagation delay with respect to the first and second input signals. The logic circuit can be used to form a decoder circuit that has a balanced propagation delay for the input signals and a minimized input capacitance. The above described logic circuit can also be changed accordingly to implement a logic NOR function.