US 6,166,571 AGranted

High speed frequency divider circuit

AssigneeLucent Technologies Inc.

InventorHongmo Wang

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Abstract

A high frequency divider circuit for producing output signals of half the frequency of an input clock signal includes two identical circuit sections, each producing an output signal and its complement. The circuit sections are connected to each other so that the output signals of one circuit section serve as input signals to the other circuit section. Each circuit section contains a load transistor which is controlled by one of the clock signal and the clock signal complement, and a switch transistor which is controlled by the other of the clock signal and the clock signal complement. The inventive circuit exhibits a reduced RC time constant for each circuit section and an increased output signal swing between the output signals and their respective complements, as contrasted with prior art frequency dividers, thereby increasing the overall circuit response time and its ability to operate at high frequencies.

A frequency divider circuit for receiving an input clock signal having a frequency value and for producing signals having a frequency value substantially half of the frequency value of the input clock signal, comprising:

a first circuit section receiving a first input signal comprising said clock signal, a second input signal, a third input signal and a fourth input signal, and generating a first plurality of output signals, said first circuit section having a first switch and first and second pairs of transistors having gate terminals, one transistor from each said pair being connected to said first switch and receiving, at its gate terminal, one of said second and third input signals and outputting the first plurality of output signals, and the other transistor of each said pair being connected to a common ground and receiving, at its gate terminal, one signal of a second plurality of output signals, said first switch receiving the fourth input signal comprising a compliment of said clock signal as an input signal to said first switch;
and
a second circuit section receiving a fifth input signal comprising the complement of said clock signal, a sixth input signal, a seventh input signal and an eighth input signal, said sixth and seventh input signals defining said first plurality of output signals, and said second circuit section generating said second plurality of output signals comprising said second and third input signals, said second circuit section having a second switch and third and fourth pairs of transistors having gate terminals, one transistor from each of said third and fourth pairs being connected to said second switch and receiving, at its gate terminal, one signal of said first plurality of output signals, and the other transistor of each of said third and fourth pairs being connected to the common ground and receiving, at its gate terminal, one of said second and third input signals, said second switch receiving said eighth input signal comprising said clock signal as an input signal to said second switch.

Abstract

Claims4