JPS6043915A - Vco circuit - Google Patents

Abstract

PURPOSE:To operate the titled circuit by a low power supply voltage by constituting the circuit with a differential pair whose current dividing ratio is controlled by a control voltage. CONSTITUTION:A couple of transistors (TRs) Q25 and Q26 constitute one differential circuit. TRs Q28, Q27 constitute the other differential circuit. The TRs Q25, Q26 are connected to a power supply VCC through switching TRs Q21, Q22 and a load resistor R22. The emitter of the TRs Q25, Q28 is connected to a ground line GND through a resistor R23 and a constant current source W21. A timing capacitor C1 is connected between the TRs Q21 and Q24. A control power supply VCONT controls the current dividing ratio between the TRs Q25, Q26 and between the TRs Q27, Q28 constituting the differential pairs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a VCO circuit, and particularly to a VCO circuit that can operate with the lowest possible power supply voltage.

[Background technology and its problems]

In conventional video signal processing circuits, an emitter-coupled vCO circuit is used as a 700 circuit (voltage controlled oscillation circuit) that can be configured on an IC circuit. Rather emitter couple mvc.

Since the yA configuration of the circuit has temperature characteristics in its oscillation frequency, it is necessary to compensate for this, and as a result, it is inevitable that the number of transistors and other elements will increase.
Since it has a configuration in which a considerable number of transistors are connected in series between the power supply and ground, there is a problem that it does not operate if the power supply voltage is low. Incidentally, since a battery is used as a power source in, for example, a portable video device, it is desirable that the power source voltage be as low as possible.

As shown in the basic circuit of Figure 1, the emitter couple gl
The V C0 circuit consists of a pair of bipolar transistors QOI
and QO2Y, whose collectors each have a load resistance Iζ1
and mV across R2. 0 and are connected to constant voltage bit sources W1 and W2 whose emitters are connected to the ground line GND, and whose emitters are connected to both Mii:VCam of a timing capacitor C1, respectively. Diodes D1 and D2 are connected to the load resistors R1 and R2 to maintain a constant current and width JCj.

&S In the structure 1y of Figure 1, the transistor QOI and Q
10 is a repeating circuit that operates on and off according to the charging and discharging operations of the timing capacitor CI. That is, time t in FIG. When transistor QOI is on and transistor QO2 is off, the collector voltage of transistor Q02 is V. 2 is ν02 = voo (1
) (Fig. 2 0), therefore, the emitter voltage of the transistor QOI and the base-emitter voltage VB of the transistor QOI become
(voltage V]), 1 = "Co-VBF, --- (21 (Fig. 2 (4)). At this time, the collector voltage of the transistor QOI.1 is the voltage drop through the diode DI. ■
List of acid pressure vci = voc that decreased by 1 ・・・・・・・・・・・・ (3
) (FIG. 2C)), which is applied to the base of transistor QO2. At this time, transistor QO2 is off, so its emitter voltage, etc. is determined by the charging voltage of the capacitor C1, and decreases as this charging voltage is discharged by the current 9 flowing through the constant current source W2.

This state is the emitter voltage of off transistor QO2 -
2 is the base-emitter voltage VB with respect to its base voltage.
It is maintained until it decreases by E. Eventually, at time t in Figure 2
1, the emitter voltage N2 is applied to the base voltage 'v01 (at this time it is V..-'VDK), and v8I! , the voltage VII, 2=vo. −
-1VD・・・・・・・・・(When it reaches 41, transistor QO2 turns on, and as a result, transistor QO2 turns on.
O2 collector voltage V. 2 is 11!1 of diode D2
The directional drop voltage VD decreases to ■o2-voo -V
ゎ ・・・・・・・・・・・・ (5) This is given to the base of the transistor QOI. At this time, the transistor QOI has a bias of 4. - Since the state is such that the collector's torque is turned off, the collector's tortoise pressure V. 1 or vol-VoO・・・・・・・・・（6）t
As the voltage increases, the emitter voltage V□11 increases by the voltage VD charged in the capacitor C1 with respect to the voltage V8. -voo-VB1+v9・・・・・・・・・・・・
・(7) IRC TC.

σ) transistor (, JOl emitter voltage Vll,
1 is the light of the capacitor C1..., the voltage is constant current source W
When it is discharged by the width of 1 - 1,Tt'', it decreases accordingly and goes to 7. Eventually, at time t2 in FIG. The base-emitter voltage VBE is lower than the voltage V, , = V, c-VB, −V, ・=−−−= (8
), transistor Qo1 turns on in the same way as transistor QO2 operates at time t1.

At this time, the collector and base of the transistor QO2 have the same voltage vc2-vcc-屹 (9
) VC! =vco-VD,・・・・・・・・・・・・ (
10) is given, so transistor QO2 turns off, and soon its emitter voltage vF, □ becomes voltage VB, 1V.
Basically, the charging voltage VD of the capacitor C1 is further reduced (same situation as described above for time t).

Thus, at time t3, transistor QOI turns off and transistor QO2 turns on again.
Thereafter, the above-described operation is repeated in the same manner.

Thus, for example, the voltage change at the collector of the transistor Q, 02 is output to the output terminal U. This is the oscillation output signal that is derived from the IJT. You can get it by closing it.

Here, the liftoff output signal V. The period T1 is determined based on the discharge time of the timing capacitor C1, and the period T1 of the capacitor C
The relational expression Q-2VDC1 for the light basket of 1 is 2 in (11)! The relationship becomes [yl], and the oscillation controller imitation f. becomes the σ) relationship.

As can be seen from equations (12) and (''3), the first
The oscillation frequency f of the 760 circuit with the configuration shown in the figure. and period T1, forward drop voltage VD'j of diodes DI and D2 (
Determined by the containing expression. However, since the forward drop voltage VD of the diodes 1)1 and D2 has a temperature characteristic, this temperature characteristic directly appears as a temperature characteristic in the oscillation frequency f and the circuit IT.

To solve this problem, as shown in Figure 3, the out-of-plane circuits of resistors R13 and Wl4 are connected between the terminal V. and the ground line GND, and the reference point is A circuit has been proposed in which the voltages 1 and 2 are obtained and this reference voltage v1 is used as the charging/discharging voltage of the capacitor C1.

In FIG. 3, transistors Q6 and Q7 which operate differentially with respect to each other are provided, and their emitters are commonly connected through transistors Q8 and Q9'a', respectively, so that a constant voltage @,
Connected to hW11. Also transistors Q6 and Q
7 through transistors Q2 and Q3Y, respectively. Connected to 0. A reference voltage V1 is applied to the bases of these transistors Q2 and Q3.

The base of one transistor Q6 is connected to the power supply V through a transistor Q5 whose base is connected to the collector of a transistor Q7. oVC connected and transistor Q7
The base of is connected to the power supply through a transistor Q4Y whose base is connected to the collector of transistor Q6. It is connected to the. The bases of these transistors Q4 and Q5 are connected through a diode Dll)r and a resistor R11, respectively.
and R12) i through the power supply V. 0, thus transistors Q4 and Q5 are kept on at all times.

Note that Wl2 and Wl:3 are constant current sources that serve as a voltage source for the transistors Q5 and Q4.

In addition to this T+, a timing capacitor C1 is connected between the emitters of transistors Q6 and Q7, and a capacitor CI is connected across transistors Q8 and Q'1 in response to changes in the voltage across this capacitor C1 and therefore in the emitter voltages of transistors 06 and Q7. transistors Q6 and Q7).
It is designed to operate k on/off l + υ. The synchronization of the on/off operations of the transistors Q6 and Q7 is controlled according to the change in the input control voltage (2) applied to the base of the transistor Q8 with respect to the reference voltage v3 connected to the base of the transistor Q9.

In the configuration shown in FIG. 3, at time t11 in FIG. 4, transistor Q6 is off and transistor Q7 is on.
Let's say it's done. When transistor Q3 is on and transistor Q2 is off. Therefore, the potential V at the base of transistor Q6. 6 (Figure 4 (At)
are reference voltage V1, transistor Q3, transistor Q5
Through the thread of VB6 = vcO-2vBm ”1 --
・-(14), whereas the base voltage VB7 of the transistor riff (Fig. 4 (B)) is 1 current nk VOO%
Through the system of diode Dll, resistor R11, and transistor Q4, VB□=vo. -Bar ・・・・・・・・・・・・
... becomes (15). Note that the value of 2V in equation (14) is the base-emitter voltage VB of transistors Q3 and Q5.
elt, and (15) Equation (1) 2 ′vf
l, ) Therefore, the emitter voltage VF,7 (FIG. 40) of the transistor Q7 in the on state is a voltage v,,=Vo, which is lower than the base voltage VB7 by the base emitter voltage VI]8. −3V,, −・−・−= (16). On the other hand, the emitter voltage of the transistor Q6 which is in the off state, etc. (Fig. 4 (C)) is determined by the charging voltage of the capacitor CI, and at time t11 (1 & m v = V -3 V + V ......
(17) 15 COBE 1 From then on, as time passes, the capacitor C1 is discharged at the peak of discharge @b1, so that tl decreases linearly.

This state continues for the interphase Tll, and eventually at time t12, the emitter voltage V of the transistor Q6 is a voltage lower than the capacitance voltage VB6 (-v.o-2VI38-vl) by one base-emitter voltage VBW (=Vo.- 3-
riv, )k(-jc 6, this transistor Q6 turns on from the off state. At this time, the emitter voltage of the transistor Q6 rises. The emitter voltage of the transistor Q6 is forced to rise to a voltage lower than the base voltage VB6 by the base-emitter voltage VBB. made to do 4
), so the emitter voltage Vl of transistor Q7 is increased by this amount,
7 or capacitor CRY to be raised VC
f, rs, and transistor Q7 are turned off. As the transistor Q6 turns on in this manner, the transistors 92&S turn on, and as the transistor Q7 turns off, the transistor Q3 turns off VC. Therefore, the base acid i17' of transistor Q6, V81=
is Denei V. v136 = ”aa 2 V through the system of o1 diode Dli, resistor R12, and transistor Q5
BF, --Moe (18), while the base potential v3□ of transistor Q7 is the base voltage ■1, following the thread Z of transistors Q2 and Q4, VB7"voo-ha'BE"1 ・−・−・=・=
It becomes (19).

Therefore, the emitter voltage Vlc6 of the transistor Q6 at time t1° is a voltage lowered by the base-emitter voltage V'BIC from the base voltage (B6' = "C6 - C)" = "00""Bl!" i...
. . . (slope), and thus the potential η6 has suddenly increased by the voltage v1 at time t□2. Therefore, the emitter voltage of transistor Q7 increases by this increase (1) through capacitor C, so that 7=Vo. -3VB, 10V, --・------
・= (21).

(18) or 21) (14) or 17
), it is clear that the operating conditions at time t1□ are the same as those at time t11 when the conditions of transistors Q6 and C7 are switched. Therefore, the circuit shown in FIG. 3 is exactly inverted from the state at time t11 at time t□2.

In this state, capacitor C1 & Nidoranjis JQ9
'd3: bii-''f release. ,,Okay. Therefore, the emitter voltage of transistor Q7 drops almost to the inside of the gate. This state (1 second T1
, continues for the period t13, and eventually at time t13, when the emitter potential N of the transistor Q7 decreases from the base potential -6 by the base-emitter voltage V, the transistor Q7
turns on and works. Thus, transistor Q6 is inverted to the OFF state in the same way as described above for time t1□, and thus the circuit of FIG.
is reversed to a state similar to that described above.

Similarly, each time T11 elapses, transistors Q6 and C7 repeat the inversion operation, so that, for example, the base potential 'vB7 of transistor Q7 changes to
When 7 is on ■. o-2VB, high potential (logical rHJ
V when the transistor Q7 turns off. 0 2-V1 low potential (logical r
This can be sent out as the oscillation output code 1 by utilizing the fact that Z becomes the oscillation output (corresponding to the LJ level).

By the way, in this case, the discharge time T1□ of the capacitor CI is , the frequency f of the chest wave number output S5. It can be expressed as .

As can be seen from equations (22) and (23), the oscillation output signal V. The formula representing the frequency and synchronization in □ does not include any elements having temperature characteristics. Incidentally, since the base voltage M is obtained by dividing it by the resistors R13 and R14, it has no temperature characteristics. Therefore, according to the configuration shown in Figure 3,
A 700 circuit which compensates for the temperature characteristics in the basic configuration shown in FIG. 1 can be obtained.

However, according to the configuration shown in FIG. 3, the power supply voltage V. . Since there are quite a large number of transistors inserted in series between the ground and the ground, the power supply voltage VooO) is required to completely connect these transistors to 1% tVao.
The voltage must be selected to be quite high. When the transistor Q7 in Figure 3 is turned on, the power supply V is applied. Diode Dll - Resistor R11 - Transistor Q4 as one of the 4-way paths from 0 to ground
-Q7-Q9 A system of constant current source Wll (consisting of an exclusion transistor) is formed, and in order to operate this system, VC is 9 (V) & 8 degrees power supply voltage V
. 0 is required.

In addition to this, according to the configuration shown in FIG.
fM'4-, the number of elements must be increased considerably, and the overall structure of this valve must become large.

[The Eye of Invention: Misfires] was created taking the above points into consideration, and is
. By reducing the number of transistors inserted between Q) and ground, the voltage required as the power supply voltage Voo can be reduced as much as possible, and the number of elements constituting the circuit can be reduced as much as possible. The aim is to simplify the overall configuration by

[Summary of the invention]

In order to achieve this object, the present invention includes a timing capacitor connected between the emitters, a first transistor and a second transistor that operate inverted with respect to each other in accordance with the charging and discharging operations of the timing capacitor, and a timing capacitor that operates on and off in response to these transistors. fifth and sixth transistors connected in series to the third and fourth transistors; and fifth and sixth transistors connected in series to the third and fourth transistors; The sixth transistor is connected to the seventh transistor forming a differential pair, and the differential operation between the fifth and sixth transistors and the seventh transistor is used to calculate the current shunt ratio? By controlling the change, the wave number and period of the oscillation output signal can be changed.

〔Example〕

Hereinafter, an example of the fabric of the present invention will be described in detail with reference to FIG. Fifth
In the figure, Q25 and Q26 are connected to one side of the differential circuit.
A pair of transistors, Q25 and Q2, are used to configure the differential circuit lft5 on the other side, and transistors Q25 and Q2 configure the differential circuit lft5 on the other side.
() are switch transistors Q21 and Q2, respectively.
4. Negatives common to 2Y. Power supply Vo through W resistor R21
connected to o. Similarly, the transistors Q27 and Q28 constituting the other differential pair are connected to the power supply V through the switch transistors Q2:3 and Q24, respectively, and the common resistor R22. Connected to 0. The emitters of the transistors Q and Q28 are commonly connected to the ground line GNDK through the emitter resistor R23 and the constant current trace WzIY, and the emitters of the transistors Q26 and Q27 are commonly connected to the ground line GNDK through the emitter resistor R23 (! Ground line G through power source W21Y
N l). Note that the constant current source W21 is driven by a drive circuit consisting of a constant current source W22 and a diode D2. Switch transistors Q21 and Q
The base of 22 is connected to the collectors of transistors Q23 and Q2A, and the base of transistors Q23 and Q24
The base of is connected to the collectors of transistors Q21 and Q22.

Further, a timing capacitor C1 is connected between the emitters of transistors Q2J and Q2/I.

Furthermore, a resistor R2 is connected to the base of the transistor Q5 and Q addition.
The bias voltage V1o is connected through 6 and resists the bases of transistors Q26 and Q27σ, along with r and R2.
A bias voltage (tsi vlo or b;
'fpiω■ooNT is connected and this control cable V. O
The shunt ratio between transistors Q25 and 026θ) configured as a differential pair by NT, transistors Q27 and Q28
The component force between.

The ratio is controlled.

In the configuration shown in FIG. 5, the transistors Q2], Q22, Q23, and Q24 are turned on and off according to the charging and discharging of the timing capacitor c1 (f/). That is, as of the time shown in FIG. , QO, Q24 is in the off state e, 1 - then 1
・Emitter voltage of transistor Q2] (Fig. 6 (A
)) is Ayano v. . - Resistor R22 - Base-emitter of transistor Q21 is connected to v□--■. O'BIG ・・・・・・・・・・・・
(24) VC'/:c>, . With respect to this VC, the emitter voltage V, 4kj,
210) 'tt 1Ar-! LK J: tte 1
ft S Fb 7:r K So'L gradually decreases to 7.

Collector voltage V1 of transistor Q2 for this purpose
, 2□ is resisting +, the voltage ΔV ΔV--! -! -■<21-■1・l(・・・・・・・・・
... Only (δ) comes out: 'O? Pressure V to 1. Voltage VC21 below 0 = VQC! −Δv・・・・・・
・・・・・・(26)Ktcru. On the other hand, the collector 'Lb' of transistor Q24 is V. 24, transistor Q24 is off, so vc24 = vo(,・
・・・・・・・・・・・・・・・ (27) Vc /'r
heart.

Here, on the fixed side, '64i W 21, the emitter resistance RB,) transistor Q25, transistor Q, when transistors Q21 and Q22 are on,
2I through i->11”k shunt and emitter resistor ■ζ series, transistor Q26, transistor Q22
Through Y, divide ttfM with U≦rim. 1 of these
Since the kL current flows through the load resistor R21 in common, the current flowing through the load resistor R21 is, and by selecting the resistance value of the resistor R2 to be 2H, the voltage drop ΔV based on the above equation (25) can be obtained. It turns out. Thus transistor Q25. Q26 is a transistor Q21. When Q22 is turned on, they operate differentially with each other, and the current shunt ratio X is the control voltage V. It will be set depending on the ONT.

On the other hand, the current (1) of the time constant current source W21 when the transistors QB and Q24 are turned on divides the current flowing through the resistor R23. These electric accents are transistors QZS and Q
24, are joined at resistor 122 VC, and the weight of fAY is 7
V-50, 2. -10. R191611, 1181,.

It becomes ). Thus transistors Q28, Q2
7 is a differential 91 operation 'a' L-, and the shunt ratio X of the mold surface flowing to each transistor is set by the tree-blocking pressure 'v0ONT.

When the emitter voltage VB24 of the transistor Q24 is the capacitor Ct or the transistor Q28'? ! tc that the current (Itjl % pressure ■. rate according to 0□7) decreases at y throughout 1''.

Eventually, at A t2 in Fig. 6, the transistor (Q
24 emitter tolerance voltage, 4 voltage applied to the base V
. 2, when the base-emitter voltage drops below VBE, the transistor Q24 turns on, thereby causing the collector voltage ■. 24 is vo24=VOo−Δ■ ・・・・・・・・・・・・
(3]), and the bias of transistor Q21 becomes 0.
Then, this transistor Q2J turns off. At this time, the collector voltage is V. 2. ■o21-V. .・・・・・・・・・・・・ (32
) rises, and this voltage is connected to the transistor Q24.
) to the base to maintain the on operation. Therefore, the emitter voltage of transistor Q24 1-I-N24H"l!i2
4 = "00" Bi ......---(:j:
<), and with this voltage 24 as a reference, the pressure boat 2 is '1f121 = Voo-VBE+Δv -=...
...-(: (4). Voltage η2 is then increased to the shunt ratio The speed decreases.

Eventually, at time t22, 'voltage n', □ or base voltage ■
When the base-emitter voltage Hv drops from o24, the transistor Q21 turns on, and at time t21, in the same way as described above, transistors Q2 and Q22 are turned on and transistors Q24 and QZ are turned off, and the state is reversed at time t11. Return to the state described above.

After that, the operation of Toro 1 is repeated, and for example, transistor Q2
・10 base voltage is oscillation output signal V. How to close j+r
, j -1'-UOLIT.

Here, the oscillation output is V. The period T of UT is expressed by the equation 1'' related to the charge of the capacitor c1 as shown in (35), and the wave number f. )
As can be seen from the equation, in the circuit of Fig. 5, the portion of the current flowing into the differential circuit is 1 ratio X, and therefore the control voltage V.ONT
The oscillation output signal V that can control the frequency of the loop 1T2□ and the wave oto is determined by the oscillation output signal V. You can see that it is a monkey to get .

Therefore, since the term having the temperature characteristic Y is not included in equations (36) and (37), the oscillation output signal V in FIG. has no temperature characteristics. And the power supply voltage V during operation. . The number of transistors that can be connected in series between the ground line GNI and the ground line GNI is only three, and therefore, in order to operate the circuit of FIG. 3 as 0
If the value is set to about [v], correct operation can be achieved without any operational problems. By the way, when transistors Q21 and Q22 turn on, the transistor that enters the column is Q2.
]-Q25-W21 and Q22-Q26-W21, and the transistor that enters when transistors Q2J and Q27K are turned on is transistor Q24-Q.
28-W21 and QB-QZ7-W2].

In addition, since the structure of FIG. 5 has a differential pair structure, it is easy to form it on an IC circuit.

Furthermore, according to the configuration shown in FIG. 5, if we look at the change in the voltage across the capacitor C1, we will see (1) as described above in FIG. 6 and (13). , -VB, K is set so that Z changes by ±ΔV with Y at the center. On the other hand, according to the conventional rental car shown in Fig. 3, the above-mentioned T
2 like “co” Vj3w ±V centered on 'a'
1 change ke (has been made, i.e. 5th)
With the 17° I attached to the transistor C1, the change in the voltage across the transistor C1 is almost constant, whereas the configuration υ in FIG.
) Field 4i & Work 3VBIL This means that it contains glue 1. This means that the combination shown in Figure 5 is in a configuration that is less susceptible to the fluctuations σ) and shadows V of the V-work compared to that shown in Figure 3. Based on this 2
(K<+≧ means that it should be improved.

Note that in the configuration of FIG. 5, transistors Q22 and Q
Even if the emitters of Z:3 are connected to each other, the same effect as in the case of Fig. 5) can be obtained.

In this case, when transistors Q2t and Q22 are turned on, transistor Q2(
5~HiQ 2'7 parallel circuit 11 circuit or differential operation 1'' transistor gain St IA: and transistor Q
24. QZ is turned on, and a parallel circuit of transistors Q26 and QZ7 constitutes a transistor that operates differentially with respect to transistor Q28. By using the same transistor for both inversion and differential operation in this way, a VCO circuit with well-balanced oscillation operation can be obtained.

In this modification, transistors Q26 and QZ7 are
A similar effect can be obtained by replacing the transistor with one transistor. - [Effect of the invention] As described above, according to the present invention, the control voltage ■ooI
By adopting a differential pair configuration in which the Mt ratio is controlled by 4T, it is possible to operate with a much lower power supply voltage than in the conventional case, and the VCO circuit does not have temperature characteristics, making it a rare element. can be easily configured. In this way, it is possible to obtain a VCO circuit that is easy to form on an IC circuit and that can be expected to improve secondary designs.

[Brief explanation of drawings]

Figure 1 is a transfer diagram showing the basic circuit of the emitter-coupled VCON path, and Figure 2 shows the signals of each part.
Figure 3 is a diagram of the 700 circuit proposed in the past, and diagram JJ44 is a diagram of the 700 circuit proposed in the past.
Figure 5 is a connection diagram showing an example of the VCO circuit according to the present invention, and Figure 6 is a connection diagram of each part of the VCO circuit according to the present invention.
-I is a signal waveform diagram. 21. S22, Q23, Q24...Switching transistor, (Q2, t, 7.26),
(Q28, Q27)...Difference I (1 transistor. Application fee m1 person)

Claims (1)

[Claims] (al) A first capacitor in which a timing capacitor is connected between the emitters and inverts each other according to the charging and discharging operations of the timing capacitor.
and a second transistor, (b) each of the above first transistors.
and third and fourth transistors that turn on and off in response to the second transistor; (cj fifth and sixth transistors connected in series to the first and second transistors; (di a seventh transistor connected to the third and fourth transistors and forming a differential pair with the fifth and sixth transistors, respectively; A 700 circuit characterized in that a control voltage for controlling a change in current division ratio in the differential pair is received between the seventh transistor and the seventh transistor.