JPH021622A - Current output circuit for phase locked loop - Google Patents

Abstract

PURPOSE:To obtain a stable output current with simple constitution and to widen the looking range of a phase locked loop with large current gain by setting an adjustment current source and first-fourth current mirror circuits to a specified combination. CONSTITUTION:The first current mirror circuit CUR1 which obtains the two output currents of a value that is proportional to a current from the adjustment current source 21, the second current, mirror circuit CUR2 to which one output current is supplied and which obtains one proportional output current, the third current mirror circuit CUR3 to which the other output current of the circuit CUR1 is supplied and which obtains two proportional output currents and the fourth current mirror circuit CUR4 to which one of the output current of said current is supplied and to which the output node of CUR2 is connected to an output node are provided. The other output of the circuit CUR3 is set for controlling the frequency of a voltage controlled oscillator 22, and a feedback signal by the phase comparison of an oscillation output and an external signal is supplied to the control node of an output element. The output current is stably maintained by the second and fourth current mirror circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a phase-locked loop current output circuit used, for example, in an audio multiplex signal processing circuit.

(Prior Art) Conventionally, there is a phase-locked loop as shown in FIG. The output of the voltage controlled oscillator 11 is phase-compared with a reference frequency signal in a phase comparator 12.

The phase error output obtained by the phase comparator 12 is smoothed by a loop filter 13 and fed back to the oscillation frequency control terminal of the voltage controlled oscillator 11 via the current output circuit 14.

Current output port F#114 is connected to transistors Q21 and Q22.
The phase error output is supplied to the base of transistor Q22. A reference voltage vrer is applied to the base of the transistor Q21.

The common emitters of transistors Q21 and Q22 are connected to ground potential through a resistor, and the collector output of transistor Q22 is supplied to a current mirror circuit composed of transistors Q23 and Q24. The collector output of transistor Q24 is supplied to a current mirror circuit composed of transistors Q25 and Q26. On the other hand, the collector output of transistor Q21 is
It is supplied to a current mirror circuit consisting of 8. The collector outputs of transistors Q26 and Q28 are commonly connected in feedback to the base of transistor Q22.

Furthermore, a transistor Q29 having a current mirror relationship with transistor Q23 is provided. Also transistor Q
A transistor Q32 having a current mirror relationship with 27 is provided, and the collector output of this transistor Q32 is as follows.
It is supplied to the collector and base of a transistor Q31, which forms a current mirror circuit together with a transistor Q30. The collector of transistor Q31 is connected to the collector of transistor Q29, and the output of this portion is supplied to the control terminal of voltage controlled oscillator 11. Note that transistors Q33 and Q34 are different! It is for collecting runoff power.

In the current output circuit 14 described above, assuming that the frequency of the reference frequency signal and the output of the voltage-controlled It is balanced, and the base voltage of each transistor Q22 is equal to the reference voltage Vr.
It is the same value as ef. At this time, transistor Q28
The collector currents of transistors Q29 and Q26 are almost equal, and the potential at point A in the figure does not change.Therefore, the collector currents of transistors Q29 and Q30 are also equal, and there is no change in the output current Iout.

Here, when the frequency of the reference frequency signal fluctuates and the output of the phase comparator 12 changes, the base potential of the transistor Q22 changes, and the resulting current flows to the transistor Q2.
3, is fed back to transistor Q26 via Q24 and Q25. Then, the collector current of transistor Q26 increases or decreases to maintain the base potential of transistor Q22 constant.

On the other hand, a current change similar to the change in the collector ti of the transistor Q2G occurs in the collector of the transistor Q29. In response to this change, the collector current of transistor Q3G is maintained constant, so that the current change that occurs in the collector of transistor Q29 is equal to the output current 1ou
t and is fed back to the control terminal of the voltage controlled oscillator 11. Therefore, the oscillation frequency of the voltage controlled oscillator 11 is controlled to maintain a constant relationship (for example, the same) with the reference frequency.

Here, the adjustment current source 15 is for adjusting the oscillation frequency (free run oscillation frequency) of the voltage controlled oscillator 11 in the balanced state of the circuit.

The reason why one adjustment current source 15 is provided independently is because if it is superimposed on the output current, it may be affected by the original fluctuation component and even the aI5 rectified current current flow) may be fluctuated. It is.

The reason why the adjustment is necessary is to adjust the deviation in the free run frequency of the voltage controlled oscillator itself and the characteristics of the circuit itself. Also, using an FM signal as the reference frequency signal,
This is because when this phase-locked loop circuit is used as a demodulation circuit that uses the phase detection output as the FM demodulation output, it is necessary to adjust the oscillation frequency of the voltage control 1 oscillator to match the frequency of the FM carrier.

(Problems to be Solved by the Invention) In the conventional phase-locked loop described above, the circuit configuration is complicated, especially since the output flow path 14 is configured by combining a differential amplifier and a plurality of current mirror circuits. It is. Furthermore, a circuit (not shown) for obtaining the reference voltage Vraf is also required, making the circuit configuration complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a phase-locked loop current output circuit whose configuration can be simplified.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a first current mirror circuit to which an adjustment current is supplied and which obtains two output currents with proportional values;
The first current mirror circuit is composed of elements of opposite polarity to the constituent elements of the first current mirror circuit, and is supplied with one output current of the first current mirror circuit to obtain one output current having a value proportional to this current. 2 current mirror circuit and an element having the same polarity as the second current mirror circuit, and is supplied with the other output current of the first current mirror circuit,
A third current mirror circuit that obtains two output currents with values proportional to this current, and one output current of this third current mirror circuit is supplied with an element having the same polarity as the first current mirror circuit. a fourth current mirror circuit, the output node of which is connected to the output node of the second current mirror circuit; For control purposes, a feedback signal based on a phase comparison result between the oscillation output of the voltage controlled oscillator and an external signal is supplied to a control node of an output element that obtains the other output current of the third current mirror circuit. It is.

(Function) With the above means, the output current that sets the free run frequency of the voltage controlled oscillator by the adjustment current is stably maintained by the second and fourth current mirror circuits, and the output current that sets the free run frequency of the voltage controlled oscillator by the adjustment current is stably maintained by the second and fourth current mirror circuits, and the output current is maintained stably by the second and fourth current mirror circuits. Only the changing component corresponding to the phase error output in the circuit is obtained as a control signal for the voltage controlled oscillator. Also, since no differential amplifier is used, the circuit configuration is simple.

A reference voltage circuit is also not required.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The adjusted current from the adjusted current source 21 is supplied to a first current mirror circuit (URI) consisting of transistors Q6 and Q7. The collector and base of transistor Q6 are connected to transistor Q
The emitters of both transistors Q6 and Q7 are connected to the power supply line. Further, transistor Q6 and transistor Q8 are also in a current mirror relationship. Therefore, the first current mirror circuit CURI can obtain two outputs.

One output of the first current mirror circuit CURI is connected to a transistor Q whose polarity is different from that of transistors Q6 to Q8.
1, the second current mirror circuit CU composed of Q2
Supplied to R2. The emitters of the l-transistors Q1 and Q2 are connected to the ground potential terminal, and a resistor R1 is connected between the bases.
, R2 are connected in series, and the connection point of the resistors R1 and R2 and the collector of the transistor Q1 are connected to the collector of the transistor Q7 (one output node of the first current mirror circuit CURL). The other output of the current mirror circuit CUR1 is a transistor Q3 having the same polarity as the transistors Q1 and Q2.

Third current mirror circuit C composed of Q4 and Q5
Supplied to UR3. Transistor Q3.

The emitters of Q4 and Q5 are connected to the ground potential terminal.

Resistors R3 and R4 are connected between the bases of transistors Q3 and Q4.
are connected, and the connection point of the resistors R3 and R4 and the collector of the transistor Q3 are connected to the collector of the transistor Q8 (the other output node of the first current mirror circuit CURI).

The third current mirror circuit CURB also obtains two outputs; the collector of the transistor Q4 (the -' side output node) is connected to the control terminal of the voltage controlled oscillator 22, and the collector of the transistor Q5 <(I!! side) output node)
are the collector of the transistor Q9 and the transistors Q9 and Q constituting the fourth current mirror circuit CUR4.
Connected to 10 bases.

The output node of the fourth current mirror circuit CUR4 (collector of transistor QIO) is connected to the output node of second current mirror circuit CUR2 (collector of transistor Q2).

The oscillation output of the voltage controlled oscillator 22 is phase-compared with a reference frequency signal in a comparator 23, and the error output thereof is smoothed by a loop filter 24 and supplied to the base of the transistor Q4.

In the above circuit, when the current amplification β is sufficiently large, the collector current I cQ2 of the transistor Q2 is I cQ2
= I adj , where I adj is the adjustment current. Now, I adj is adjusted and the free run frequency F of the voltage controlled oscillator 22
IcQ4 when vcol is equal to the reference frequency Ftno
=IcQ5 =Iadj. IcQ4 and IcQ5 are collector currents of transistors Q4 and Q5, respectively.

Next, when the reference frequency FinO changes by Δf, IcQ4
=IcQ5 =Iadj +IΔf. However, Δf is the current required to change the oscillation frequency of the voltage controlled oscillator from FinO by Δf.

Taking the difference between the currents I cQ5 and I cQ2, IcQ5-
ICQ2 = IΔf, and a current that is not superimposed on the free-run frequency adjustment current I adj can be obtained as a change in the collector current of transistor Q4. In other words,
Tone! 1 current I adj can be adjusted independently,
This current is not affected by the current of ■Δf.

Furthermore, second and third current mirror circuits CUR2 and CU
R3 is provided with resistors R1 to R4. In particular, by providing the resistor R3, the third current mirror circuit C
The impedance seen from the phase comparator 23 on the URB side does not become small, and the current gain is also large.

FIG. 2 shows another embodiment of the invention. The difference from the previous embodiment is that a transistor Q11 is added to the second current mirror circuit CUR2. Other parts are the same as those in the previous embodiment, and are therefore given the same reference numerals as in FIG. In this circuit, the number of transistors in the second and third current mirror circuits CUR2 and CUR3 is the same, the pace current environment is the same, and the DC components of transistors Q2 and Q5 are equal regardless of the magnitude of the current amplification factor β. That's what I do.

C Effects of the invention j As explained above, according to this invention, with a simple configuration,
A stable output current can be obtained, and the current gain is large and the lock range of the phase locked loop can be widened.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the invention, FIG. 2 is a circuit diagram showing another embodiment of the invention, and FIG. 3 is a circuit diagram showing a conventional current output circuit. 21...Tune 11 current source, 22...Voltage controlled oscillator,
23... Phase comparator, 24... Loop filter, C
UR1~CUR4...Current mirror circuit, Q1~Q
ll...transistor, R1-R4...resistance. Applicant's representative Patent attorney Takehiko Suzue Figure 3 1゜Indication of the case Patent Application No. 1986/1986 2゜Name of the invention Phase-locked loop current output circuit 3゜Relationship with the case

Claims (1)

[Claims] A first current mirror circuit to which an adjustment current is supplied and obtains two output currents with a value proportional to this current, and an element of opposite polarity to the constituent elements of this first current mirror circuit. A second current mirror circuit is supplied with one output current of the current mirror circuit and obtains one output current with a value proportional to this current, and an element having the same polarity as the second current mirror circuit. The other output current of the first current mirror circuit is supplied, and the third current mirror circuit obtains two output currents with values proportional to this current, and one output current of this third current mirror circuit is supplied. and a fourth current mirror circuit configured of elements of the same polarity as the first current mirror circuit, the output node of which is connected to the output node of the second current mirror circuit; The other output current of the current mirror is used to control the oscillation frequency of the voltage controlled oscillator,
A current in a phase-locked loop configured to supply a feedback signal based on a phase comparison result between the oscillation output of the voltage-controlled oscillator and an external signal to a control node of an output element that obtains the other output current of the third current mirror circuit. Output circuit.