| 摘要 |
A circuit that forms a square wave pulse train signal wherein each pulse is centered about a zero crossing of a reference sinusoid. A first capacitor is coupled to be charged and discharged at equal rates by a first transconductance amplifier. Upon a first positive zero crossing of the reference sinusoid, the first transconductance amplifier begins charging the first capacitor. Upon the first negative zero crossing, the first transconductance amplifier begins discharging the first capacitor until a first predetermined voltage level is reached. Upon reaching the first predetermined voltage level, the first transconductance amplifier begins charging the first capacitor again. The voltage on the first capacitor is compared by a first comparator to a second predetermined voltage level higher than the first voltage level. The output of the first comparator is a pulse which is centered about a second positive zero voltage crossing of the reference sinusoid. The voltage on the first capacitor is discharged until a third positive zero crossing of the reference sinusoid when the cycle begins again. A second capacitor is coupled to be charged and discharged by a second transconductance amplifier. Upon the second positive zero crossing of the reference sinusoid, the second transconductance amplifier begins charging the second capacitor. A second pulse is formed centered about the third positive zero crossing in the same manner as the first pulse. The pulses are combined into a single signal forming a train of pulses wherein a pulse is centered about each positive zero crossing of the reference sinusoid.
|
