CN-122001302-A - Differential cross-coupled multivibrator

CN122001302ACN 122001302 ACN122001302 ACN 122001302ACN-122001302-A

Abstract

The invention belongs to the field of analog integrated circuit design, and particularly relates to a differential cross-coupling multivibrator, which comprises an oscillation main circuit, a control voltage selection circuit, a control voltage buffer circuit and an auxiliary control voltage selection circuit, wherein the oscillation main circuit is used for generating periodic rectangular waves, the control voltage selection circuit is used for realizing frequency adjustment of the oscillation main circuit by selecting control voltage, the control voltage buffer circuit is used for inhibiting power noise interference in the oscillation main circuit and assisting the control voltage selection circuit in realizing frequency adjustment, the frequency of an oscillator can be changed along with the change of voltage by introducing the control voltage selection circuit, the effect of a voltage-controlled oscillator is realized, and the influence of process deviation is reduced by introducing the control voltage buffer circuit.

Inventors

ZHU LING
CHEN PENGFEI
LIU LU
CHEN SILIANG
HU YUN
HU YONGFEI
NI YABO

Assignees

重庆吉芯科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260122

Claims (8)

1.A differential cross-coupled multivibrator comprising: an oscillation main circuit for generating a periodic rectangular wave; The control voltage selection circuit is used for realizing the frequency adjustment of the oscillation main circuit by selecting the control voltage; and the control voltage buffer circuit is used for inhibiting power supply noise interference in the oscillation main circuit and assisting the control voltage selection circuit to realize frequency adjustment.
2. The differential cross-coupled multivibrator of claim 1, wherein the control voltage selection circuit comprises switches S1-S3, resistors R1-R4, and capacitor C1, wherein: One end of the resistor R1 is connected with the voltage Vin, and the other end of the resistor R1 is connected with one end of the resistor R2, the other end of the resistor R2 is connected with one end of the resistor R3, the other end of the resistor R3 is connected with the resistor R4, and the other end of the resistor R4 is grounded; the switch S1 is connected to two ends of the resistor R2, the switch S2 is connected to two ends of the resistor R3, and the switch S3 is connected to two ends of the resistor R4; one end of the capacitor is connected with one end of the resistor R2 and controls the voltage buffer circuit, and the other end of the capacitor C1 is grounded.
3. The differential cross-coupled multivibrator of claim 2, wherein resistors R2-R4 have equal resistance and R1 has twice the resistance of resistor R2.
4. The differential cross-coupled multivibrator of claim 2, wherein the control voltage buffer circuit comprises transistors Q7-Q10, wherein: The base of the transistors Q7-Q8 is connected with a capacitor C1 in the control voltage selection circuit, the connection point is marked as V1, the collector of the transistor Q7 is connected with a power supply voltage, the emitter of the transistor Q7 is connected with the base of the transistor Q9 and the oscillation main circuit, the collector of the transistor Q9 is grounded, the emitter of the transistor Q9 is connected with the emitter of the transistor Q10, the connection point is marked as V2, the emitters of the transistors Q9-Q10 are also connected with the oscillation main circuit, the collector of the transistor Q8 is grounded, the emitter of the transistor Q8 is connected with the oscillation main circuit, the base and the collector of the transistor Q10, and the collector of the transistor Q10 is connected with the power supply voltage.
5. A differential cross-coupled multivibrator as claimed in claim 4 wherein transistors Q7, Q10 are NPN transistors and transistors Q8, Q9 are PNP transistors.
6. The differential cross-coupled multivibrator of claim 1 or 4, wherein the oscillating main circuit comprises resistors R5-R6, transistors Q1-Q6, capacitor C, current source I1-I6, wherein: The input end of the current source I1 is connected with the power supply voltage, and the output end of the current source I1 is connected with the collector electrode of the transistor Q8; The output end of the current source I2-I6 is grounded, the input end of the current source I2 is connected with the emitter of the transistor Q3 and the base of the transistor Q2, the connection point between the base of the transistor Q2 and the input end of the current source I2 is used as a first output end of the differential cross-coupling multivibrator, the input end of the current source I3 is connected with the emitter of the transistor Q1 and one end of the capacitor C, the input end of the current source I4 is connected with the emitter of the transistor Q7, the input end of the current source I5 is connected with the emitter of the transistor Q2 and the other end of the capacitor C, the input end of the current source I6 is connected with the emitter of the transistor Q4 and the base of the transistor Q1, and the connection point between the base of the transistor Q1 and the input end of the current source I6 is used as a second output end of the differential cross-coupling multivibrator; The collector of the transistor Q1 is connected with the base of the transistor Q3, the emitter of the transistor Q5 and one end of the resistor R5, the other end of the resistor R5 is connected with the power supply voltage, the collector of the transistor Q3 is connected with the power supply voltage, the base and the collector of the transistor Q5 are connected with the emitter of the transistor Q9, the collector of the transistor Q2 is connected with the base of the transistor Q4, the emitter of the transistor Q6 and one end of the resistor R6, the other end of the resistor R6 is connected with the power supply voltage, the collector of the transistor Q4 is connected with the power supply voltage, and the base and the collector of the transistor Q6 are connected with the emitter of the transistor Q10.
7. The differential cross-coupled multivibrator of claim 6, wherein resistors R5-R6 have the same resistance and current sources I1-I6 have the same current.
8. The differential cross-coupled multivibrator of claim 6, wherein transistors Q1-Q6 are NPN transistors.

Description

Differential cross-coupled multivibrator Technical Field The invention belongs to the field of analog integrated circuit design, and further relates to the field of voltage-controlled oscillators, in particular to a differential cross-coupling multivibrator. Background The emitter coupled multivibrator (Emitter-Coupled Multivibrator) is a non-steady self-oscillation circuit based on a transistor symmetrical structure, the core working principle of the emitter coupled multivibrator is that two cross-coupled transistors are alternately conducted, so that current is redistributed, state overturning is realized through charge and discharge of a coupling capacitor, and the emitter coupled multivibrator is circularly reciprocated to form continuous square wave oscillation, and the emitter coupled multivibrator is widely used for scenes such as low-frequency pulse generation, digital circuit clocks and timers. Currently, emitter coupled multivibrators suffer from the following drawbacks: the oscillation frequency can be adjusted only by adjusting capacitance, resistance or current parameters, and the frequency can not be directly controlled by voltage, so that the voltage-controlled oscillation function is difficult to realize. Circuit performance is susceptible to power supply noise. Disclosure of Invention To solve the above problems, the present invention provides a differential cross-coupled multivibrator, comprising: an oscillation main circuit for generating a periodic rectangular wave; The control voltage selection circuit is used for realizing the frequency adjustment of the oscillation main circuit by selecting the control voltage; and the control voltage buffer circuit is used for inhibiting power supply noise interference in the oscillation main circuit and assisting the control voltage selection circuit to realize frequency adjustment. The invention has the beneficial effects that: The voltage-controlled oscillator has the advantages that the frequency of the oscillator can be changed along with the change of the voltage by introducing the control voltage selection circuit. The invention introduces a control voltage buffer circuit to reduce power supply noise and reduce the influence of process deviation. The circuit has simple structure and low implementation difficulty, and is suitable for most processes. Drawings FIG. 1 is a conventional emitter coupled multivibrator; FIG. 2 is a graph of static I-V characteristics of two ports of a conventional emitter-coupled multivibrator capacitor; FIG. 3 is a differential cross-coupled multivibrator of the present invention; FIG. 4 is a simulation result of the output of the differential cross-coupled multivibrator of the present invention; FIG. 5 is a simulation result of output frequencies of different control voltages according to an embodiment of the present invention. Detailed Description The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The circuit shown in fig. 1 is an emitter-coupled multivibrator, and its structure is composed of transistors, resistors, capacitors and current sources. Depending on the parameter configuration (in particular the value of the capacitance C), the circuit may exhibit two distinct modes of operation, a relaxation oscillator mode and an approximately sinusoidal LC oscillator mode. When the value of the capacitor C is large, the circuit operates in a relaxation oscillator mode, and when the value of the capacitor C is small, the circuit operates in an approximate sine LC oscillator mode. Since emitter-coupled multivibrators are mostly used to generate clock signals, the invention will be discussed only with respect to relaxation oscillator modes. In the relaxation oscillator mode, the basic working principle can be described as that two ends of a connecting capacitor C are regarded as a nonlinear two-port network, and the characteristic curve is S-shaped after derivation, as shown in fig. 2, wherein I represents the current flowing through the capacitor C, and V represents the voltage across the capacitor C. The relaxation oscillation is essentially a process that the capacitor repeatedly charges and discharges between two unstable critical points, and a complete working period can be divided into the following four phases: Stage one (capacitor charging from point D to point a) assuming the initial time the circuit is operating at point D on the upper right branch of the S curve, where Q2 is nearly off and Q1 is conducting most of the current. The capacitor C starts to charge through the left-hand pa