Phase interpolator

Abstract

A phase interpolator includes a first to a fourth differential pair. Each of the differential pairs includes a first and a second transistor and a stabilizing capacitor connected between a source coupled node and a reference voltage. The phase interpolator also includes a plurality of current sources and a group of switches to switch connections between the source coupled nodes of the differential pairs and the current sources so that (i) a first operating current is supplied to a first selected one of the first and second differential pairs and (ii) a second operating current is supplied to a second selected one of the third and fourth differential pairs. Drains of the first transistors in the differential pairs are commonly connected and drains of the second transistors in the differential pairs are commonly connected to form a first and a second output node so that a differential output signal is output.

Description

technical field

[0001] The present disclosure relates to phase interpolators that interpolate between phases of a plurality of differential input signals to produce a differential output signal having a desired phase. Background technique

[0002] Figure 12 is a circuit diagram showing the construction of a known phase interpolator. Figure 12 The phase interpolator 32 shown in FIG. 2 receives input signals I, Q, Ib, and Qb, which are four-phase signals that are 90° out of phase with each other. That is, the phase interpolator 32 divides the entire cycle of the reference clock signal into first to fourth quadrants with the input signals I, Ib, Q, and Qb, as Figure 13 is shown in , and interpolates between the phases of these input signals.

[0003] Phase interpolator 32 includes four differential pairs 12-1 to 12-4, sixteen current sources 14-1 to 14-16, a set of switches 16, and two load resistors 18A and 18B . Each of the differential pairs 12 - 1 to 12 - 4 includes t...

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