JPS60169215A - Oscillator - Google Patents

Abstract

PURPOSE:To make the oscillated amplitude constant by constituting an n-stage of ring oscillator in the unit of amplifiers comprising a voltage amplfier and a current amplifier and varying a current of an optional number of current amplifiers among the n-stage of the current amplifiers so as to vary the oscillating frequency. CONSTITUTION:The circuit from a common base 11 of transistors (TR) Q5, Q6 being a constant current load of an emitter follower of the 1st stage to a common base 12 of TRs Q11, Q12 being a constant current load of the n-th stage is connected to a terminal 13 so as to set the control range at a frequency control terminal 15 via a control voltage shift circuit 14 and in the constitution above, the oscillating frequency is decided in inversely proportion to the delay time of the oscillating loop. Thus, in varying a current of a TRQ4 to vary the phase of TRs Q1-Q4 for example, the impedance viewed from the base is changed and since the base is connected to a high resistance resistor R1 of the collector of the TRQ1, the phase is changed largely. Since the voltage amplification is constant in the emitter follower, the frequency is changed largely while keeping the oscillating level.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a frequency controllable ring oscillator type oscillator which is necessary for a digital signal processing circuit and is a means of a lock generator.

Configuration of a conventional example and its problems FIG. 1 shows a conventional example in which frequency control is performed using a general ring oscillator. Generally, voltage amplifiers (inverting amplifiers) are connected in n stages (A+ to An) so that the stages are an odd number.
The output of the n-stage amplifier An is fed back to the input of the first-stage amplifier A1 to form an oscillation loop. It is configured to output from 2. The oscillation frequency is a frequency that is inversely proportional to nτ, where τ is the delay time per amplifier stage. Normally, the oscillation frequency is varied by varying the amplifier current, which is a function of the delay time τ.

For example, as shown in FIG. 1, a common configuration method is to connect the current variable terminals a1 to al of each amplifier and to vary the frequency at the oscillation frequency variable terminal 3.

In recent years, clock frequencies have become higher, and it is possible to stabilize or lock the frequency by dividing the clock using a high-frequency voltage-controlled oscillator (VCO) and applying phase-locked loop (PLL) locking in the low frequency region. many.

The following problems can be considered when a variable frequency ring oscillator as described above is used as the vCO in this case. First, since the amplification rate changes by changing the current of the amplifier, the oscillation level also tends to fluctuate by changing the frequency. Second, since the distortion characteristics change by changing the current of the amplifier, the harmonic level of the oscillator tends to fluctuate by changing the frequency. This will adversely affect radio wave interference and circuit operations at a stage before the TL clock, which is oscillation in the high frequency range, is shaped. Thirdly, for the first and second reasons mentioned above, when creating a vCO with a constant oscillation level and few harmonics, the frequency variable range becomes narrow. 'Object of the invention The present invention is a ring oscillator type V which eliminates the drawbacks of the conventional example.
The aim is to provide CO. That is, the present invention provides a VCO in which the oscillation level is constant, the harmonic level is low, there is little variation, and the oscillation frequency can be varied over a wide range.

Furthermore, there is no determining factor for the oscillation frequency other than the control terminal of the VCO, making it a so-called non-adjustable oscillator, which can be effectively used especially in a high frequency region, and is ideal for IC implementation.

Structure of the Invention The present invention provides a ring oscillator in which an amplifier including a voltage amplifier and a current amplifier is used as one unit, and n stages of odd or even number of amplifiers as described above constitute a ring oscillator. n of current amplifier
The structure is such that the oscillation frequency can be varied by varying the current of one or more current amplifiers in the stages.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows a block diagram showing the basic configuration of the present invention. In the figure, B1 to Bn are voltage amplifiers, and 01 to Cn are current amplifiers. The configuration is such that the first voltage amplifier B1 is followed by the first current amplifier C1, and B and +Cj are sequentially connected as a one-stage amplifier to form an n-stage configuration. (n is odd or even number).

Then, the output of the nth stage current amplifier is fed back to the input of the first stage voltage amplifier to form an oscillation loop, and the required oscillation level is output from the output terminal 6 via the output amplifier 4. The configuration is such that the output can be extracted.

The frequency variable configuration connects the current variable terminals C1 to an of the current amplifiers 01 to On to vary the frequency by the frequency variable terminal 6. By varying the current of the current amplifier, the gain hardly changes and the delay time (phase)
Therefore, if the bias condition of the amplifier during the oscillation nope is set to a condition that lowers the harmonic level, the oscillation level will change in a ring oscillator configured as shown in Figure 2. It is almost constant, the harmonic level is low, and there is little fluctuation.
Furthermore, a vCO with a wide frequency variable range can be realized.

Next, a specific embodiment of the present invention is shown in FIG.

In the figure, the emitters of transistors Q5Q2 having a differential amplification configuration are connected to a common current source 7, and the collectors of each transistor are connected to load resistors R1 and R2, respectively.
It is connected to the base of each of emitter-follower transistors Q4 and Q5. Furthermore, the emitters of each of transistors Q5 and Q4 are connected to a constant current load formed by transistor Q5 and resistor R5, and to a constant current load formed by transistor Q6 and resistor R4. Transistor Q...
Differential multiplier [1] by Q2 and transistors Q5 and Q4
The emitter follower constitutes an amplifier corresponding to the first stage of the ring oscillator shown in FIG. 2 described above. Similarly, the differential amplifier made up of transistors Q7 and Qa and the emitter follower made up of transistors Q9'q, . . . constitute an amplifier corresponding to the n-th stage in FIG. In this way, the emitters of each of the transistors Q, O, and Q9 of the n-th emitter follower are connected to the transistor Q1 of the first-stage differential amplifier. By connecting to each base of Q2, an oscillation loop is formed. Furthermore, transistor Q2. The emitter of Q1o is the output amplifier 13
The necessary oscillation level is output from the output terminal 14. Further, from the common base terminal 11 of the transistor Qs, which constitutes the constant current load of the emitter follower of the first stage, and the common base terminal 12'j of the transistor Q6, which constitutes the constant current load of the emitter follower of the nth stage, The frequency control terminal 15 is connected to a terminal 13 and a necessary control range is set via a control voltage shift circuit 14 at a frequency control terminal 15. 12 is a power supply terminal.

Note that Figure 3 shows the case where the oscillation loop has an odd number of stages (three stages), but in the case of an even number of stages, the connection from the balanced output of the nth stage to the balanced input of the first stage is reversed, and the phase difference is changed. If you connect it with negative feedback (inverted phase) to the ring oscillator type v
Operates as a CO.

In other words, by configuring the voltage amplifier with a differential amplifier, the number of amplifier stages can be used with either an odd or an even number.
The center oscillation frequency can be set freely, expanding the range that can be covered. .

Further, in the case of FIG. 3, the frequency range is widened by varying the currents of all emitter followers, but any number of emitter followers whose currents can be varied may be greater than 1 Vi. (You can freely set it to be variable.) Also, one unit of amplifier is composed of two emitter followers for balanced output, but one emitter follower is unbalanced and forms an oscillation loop. Good too.

Also, instead of using a differential amplifier, if you use an inverting amplifier and configure a ring oscillator with amplifiers of various configurations,
A VCO that varies the emitter follower current will function in the same manner as above. Here, the reason why the excavation frequency can be greatly varied by varying the emitter follower current in the ring oscillator having the configuration shown in FIG. 3 will be explained. The oscillation frequency is determined approximately in inverse proportion to the delay time τ of the oscillation loop. Therefore, the oscillation frequency is varied by varying the delay time or phase of the oscillation loop. For example, in order to vary the phase of transistors Q1 to Q4, by varying the current of the emitter follower composed of transistor Q4, transistor Q
The impedance seen from the base of Q4 changes, and since the base of Q4 is connected to the high resistance load R1 of the collector of Q1, the phase changes significantly here. Furthermore, since the voltage increase d] is constant in the emitter follower, it is an advantageous means because the oscillation level is constant and the oscillation frequency can be greatly varied.

FIG. 4 shows a part of a circuit of another example of a specific application of the present invention. This figure shows the circuit configuration of one unit of amplifier that forms the oscillation loop of the ring oscillator. That is, transistors Q15' and Ql4 constitute a differential amplifier, and transistors Q, 5. Q16. Q19. Q2o constitutes an emitter follower and transistor Q17'q+s.

Q21, Q22 and resistors R11, R12, R13, R
14 constitutes a constant current load of 1 misota follower.

17 and 18 are balanced input terminals, 19 and 20 are balanced output terminals, and 21 is a terminal for varying the emitter follower current. In the case of FIG. 4, all the currents in the Emi and η Tahoroa are varied, but any number may be used as long as it is one or more. Furthermore, since the current amplifier is configured with 72 stages of emitter volts, the voltage between the collector and base of the differential amplifier can be wide (vBF), and the oscillation level can be increased. In this way, the scope of the configuration of one unit of amplifier that forms an oscillation loop is expanded, and the voltage amplifier is configured with one or more stages of differential amplifiers or inverting amplifiers, and the current amplifier is By configuring the emitter follower with one or more stages of constant current load,
The range of applications can be expanded.

FIG. 5 shows the characteristics of the ring oscillator in a three-stage configuration in the specific embodiment shown in FIG.

The horizontal axis shows the control voltage, and the vertical axis shows the characteristics i of the oscillation level 22, oscillation frequency 23, and (fundamental wave-harmonic) level 24. From the figure, it can be seen that the oscillation level has little variation with respect to the control voltage, the oscillation frequency has a wide variable range, and the harmonic level is relatively low and has little variation.

Effects of the Invention As is clear from the above description, the present invention provides the following effects.

(1) In a ring oscillator that forms an oscillation loop in an n-stage configuration by arranging an amplifier (d) consisting of a voltage amplifier (d) and a current amplifier, the oscillation frequency can be adjusted by varying the current of the current amplifier. By making it variable, it is possible to realize a voltage controlled oscillator in which the oscillation level is constant, the harmonic level is low, there is little variation, the oscillation frequency can be varied over a wide range, and the oscillation frequency setting does not need to be adjusted.

(2) The effect of (1) above can be achieved by configuring one unit of amplifier in the oscillation loop of (1) above with a voltage amplifier using a differential amplifier and an emitter follower with a constant current load. In addition, the circuit configuration becomes suitable for integrated circuits. or,
Since it can be configured with a balanced oscillation loop, a ring oscillator can be configured with either an odd or even number of stages.

(3) Voltage increase rlJ by the voltage intensifier by inverting the amplification amount of one unit of the amplifier in the oscillation loop of (1) above
Even if an odd-numbered stage ring oscillator is configured with an emitter follower having a constant current load and an emitter follower with a constant current load, the same effect as the above (1) can be obtained.

(4) One unit of amplifier in the oscillation loop of (1) above is replaced by a voltage amplifier using one or more stages of differential amplifier or inverting amplifier, and an emitter follower with one or more stages of constant current load. By configuring the current amplifier using a current amplifier, the degree of freedom in design is widened in terms of oscillation level, oscillation frequency variable range, single circuit configuration, etc.

(6) Other In addition to the effects described in (1) to (4) above, it is possible to eliminate the need for inductance and capacitance elements in the oscillator configuration, which is extremely advantageous when integrated circuits are used. Become.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a voltage controlled oscillator configured with a conventional general ring oscillator, FIG. 2 is a block diagram of a voltage controlled oscillator according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. A specific circuit configuration diagram of a voltage controlled oscillator according to
FIG. 4 is a circuit configuration diagram showing another specific application example of the present invention,
FIG. 5 is a characteristic diagram of the specific embodiment shown in FIG. B, ~Bn...Voltage amplifier, C4~Cn...
...Current amplifier, C1-Cn... Current variable terminal of amplifier, 4.9... Output amplifier, 5.10
...Oscillation output terminal, 6°15 ...Oscillation frequency variable terminal, Q1-Q22 ...Transistor, R7-R14τ ...Load resistance, 7,8. 16
. . . Current source, 14 . . . Control voltage shift circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4/1 #J #l] Voltage (Vl

Claims (1)

[Scope of Claims] (1) An amplifier consisting of a voltage amplifier and a current amplifier
A ring oscillator is constructed by using n stages of unit amplifiers (fc, n is an odd number or an even number), and the current of one or more of the n stages of the current amplifiers is An oscillator characterized in that the oscillator is configured to have a variable oscillation frequency. ? 2. The oscillator according to claim 1, wherein the voltage amplifier is a differential amplifier, and the current amplifier is an emitter follower having a constant current load. (3) A patent claim characterized in that the voltage amplifier 1] is composed of an inverting amplifier 1], the current amplifier is composed of an emitter follower having a constant current load, and a ring oscillator is composed of an odd number of n stages. The oscillator according to the range (1) above. 4) The voltage amplifier is a differential amplifier or an inverting amplifier.
The oscillator according to claim 1, wherein the oscillator has a stage configuration, and the current amplifier has an n-stage configuration including an emitter follower with a constant current load.