Relaxation-type voltage-controlled oscillator

Abstract

The invention discloses a relaxation-type voltage-controlled oscillator, which is composed of a charging capacitor, a switching tube assembly, a comparison circuit, a charging current source and a logic control circuit, and is characterized by being provided with the charging current source which is formed by a constant current source and a controlled current source in parallel; the switching tube assembly is formed by a first group and a second group of four switches; the charging capacitor is connected with a first group of switching tubes and a second group of switching tubes; the comparison circuit is formed by a cross-coupled geminate transistor, and is connected with the two positive and negative ends of the charging capacitor; the cross-coupled geminate transistor comprises a firstclamper tube and a second clamper tube, wherein, the input end of the first clamper tube is connected with the output end of the second clamper tube; and the input end of the second clamper tube is connected with the output end of the first clamper tube. The relaxation-type voltage-controlled oscillator of the invention adopts the break-over voltage of a semiconductor tube as a comparison voltage, improves the oscillating frequency through improving the structure of the controlled circuit source, has high linearity, adopts a current source to avoid the consistency problem of the process, and is easier to realize.

Description

technical field [0001] The invention relates to an oscillator, in particular to a relaxation type voltage-controlled oscillator used in a phase-locked loop (PLL). Background technique [0002] In modern communication systems, phase-locked loops (PLLs) have become ubiquitous due to their outstanding versatility (universal applicability, applicability). The so-called phase-locked loop is a feedback control circuit that uses an external input reference signal to control the frequency and phase of the internal oscillation signal of the loop. When the frequency of the output signal is equal to the frequency of the input signal, the output voltage and the input voltage remain fixed. The phase difference, that is, the phase of the output voltage and the input voltage is locked, mainly composed of a phase detector, a loop filter and a voltage-controlled oscillator, of which the voltage-controlled oscillator is the core component, and its function is to generate an oscillation freque...

AI Technical Summary

Problems solved by technology

can be controlled by the capacitor C T Charge and discharge current I 1 , I 2 To control the oscillation period, but this kind of oscillator needs to generate an accurate reference voltage value externally to complete the comparison oscillation, and cannot generate differential output, and at high frequencies, due to the delay of the gate, the linearity decreases

[0005] figure 2 The relaxation oscillator shown is realized figure 1 The most traditional structure of the principle, it has a simple structure, but it needs two current sources. Due to problems such as process consistency, it is difficult to completely match the two current sources, and the operating frequency is not high.

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