Patent ID: 7091756
Filing Date: 2006-08-15
Classification: H03K

Abstract:
1. A signal generating circuit comprising: a first generating means for generating a first periodic signal; a second generating means for generating a second periodic signal which is in anti-phase with the first periodic signal; a frequency divider circuit comprising, (i) first and second input terminals for respectively receiving the first and second periodic signals; (ii) an even number of amplifier stages connected in series with an output of the last amplifier stage being connected to an input of the first amplifier stage, wherein each amplifier stage has an associated propagation delay and a transistor coupled between a supply terminal and a reference terminal for modulating the propagation delay through the associated amplifier stage; (iii) means for applying said first periodic signal received at said first input terminal to a control electrode of said transistor of the or each odd amplifier stage and for applying said second periodic signal received at said second input terminal to a control electrode of said transistor of the or each even amplifier stage, to modulate the propagation delays through the associated amplifier stages about half the period of said first and second periodic signals so that when the propagation delay through the or each even amplifier stage decreases, the propagation delay through the or each odd amplifier stage increases; and (iv) an output terminal connected to the output of said last amplifier stage for outputting a generated frequency divided signal; wherein said first and second generating means are arranged to generate the respective first and second periodic signals as analogue periodic signals having an amplitude which causes said transistors to be not fully open or fully closed but to act as variable resistances, and wherein each of the transistors of each odd amplifier stage that is used to modulate the propagation delay through the odd amplifier stage references the first periodic signal to a voltage supply, and each of the transistors of each even amplifier stage that is used to modulate the propagation delay through the even amplifier stage references the second periodic signal to the same voltage supply.