JPS6256014A - Voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To reduce number of components by giving a current depending on the control current in response to the oscillation mode so as to activate the titled oscillator at a low voltage. CONSTITUTION:Collectors of transistors (TRs) Q11, Q12 are connected to a power supply VB via resistors R11, R12, connected to the base of other TR, the emitters of the TRs Q11, Q12 are connected mutually via a capacitor C and connected to collectors of TRs Q13, Q14 and constant current sources S11, S12. The emitters of the TRs Q13, Q14 are connected to common via resistors R13, R14 and each base is controlled by a control voltage Vf. Further, the anode of diodes D11, D12 is connected to each base of the TRs Q11, Q12, each cathode of the diodes D11, D12 is connected mutually and connected to the collector of the TR Q15. The emitter of the TR Q15 is connected to common via a resistor R15 and the base is controlled by the control voltage Vf. Thus, the power voltage VB is reduced to a required value.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a voltage controlled oscillator with an astable multivibrator configuration.

[Technical background of the invention]

A voltage controlled oscillator with a conventional multivibrator configuration is used as a second
As shown in the figure. This voltage controlled oscillator is
This is described in No. 89, and transistors Ql and Q2 are mutually turned on according to the potential difference at the capacitor C end.

Oscillates while turning OFF. The control voltage Vf of the oscillation frequency is applied to the transistor Q3. One-voltage current is converted by the differential pair Q4, and one side of the differential output current of the voltage-current converter always flows through the transistors Q5 to Q8, which constitute switches that switch according to the oscillation mode. .

Also, the potential difference at the capacitor end for reversing the oscillation mode depends on the voltage drop across the resistor aX when the transistor Q1 is turned on, but a constant current In flows through the resistance ratio 1 regardless of the control voltage V. .

That is, this voltage controlled oscillator has the size of the capacitor 1c,
The oscillation frequency is determined by three elements: the current I for charging and discharging the capacitor C, and the potential difference at the end of the capacitor for reversing the oscillation mode, and as described above, the charging and discharging current I of the capacitor C is controlled,
The excavation frequency is controlled by keeping other factors constant.

[Problems with background technology] The conventional configuration described above requires a voltage-current converter for the differential amplifier and a switch that changes depending on the excavation mode, so it is not suitable for low-voltage operation and has the disadvantage of increasing the number of components. [Purpose of the invention]

The present invention has been made in view of the above problems, and an object of the present invention is to provide a voltage controlled oscillator that can be operated at low voltage and has a small number of constituent elements.

[Summary of the Invention] The present invention provides a current that depends on the control current in accordance with the oscillation mode in order to prevent the potential difference at the terminal of the capacitor C necessary for reversing the excavation mode from changing due to the control current of the excavation frequency. This allows operation at low voltage and reduces the number of constituent elements.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, each collector of a pair of transistors Q11 and Ql2 has a resistance ratio of 11. Power supply via R12
8 and each to the base of the other transistor. Also, transistors Qll and Ql2
The emitters of Q13 .
Transistor Q13.Q14 is connected to the collector of Q14.
Each emitter of Q14 is grounded through a resistor R13, and each base is controlled by a control voltage Vf. Further, the anodes of diodes DIl and D12 are connected to the bases of the transistors Qll and Ql2, respectively.
The cathodes of the diodes Dll and D12 are interconnected and connected to the collector of the transistor Q15.

The emitter of transistor Q15 is grounded via resistor R1s, and the base is controlled by control voltage Vf/.

The operation of the voltage controlled oscillator according to the present invention having the above configuration will be explained below.

Transistors Qll and Q12 are excavated by repeating alternate K ON and OFF. First, the transistor Ql
Consider the case when l is ON l and Qlz is OFF l. At this time, the current l generated by the constant current sources 811 and 812
01) Transistor Q13. All of the collector current Ic of Q14 flows through the resistor Ro. At this time, the capacity tC is Io +
A current Ic flows and the emitter potential of transistor Q12 drops until transistor Q12 is turned on. The reason for this is that the base potentials of the transistors Ql s and Ql 2 are each determined by the voltage drop across the resistor R12°Rtl.

Next, when the emitter potential of the transistor (Jz) decreases and the transistor Q12 turns on, a voltage drop across the resistor R12 occurs, and the base potential of the transistor Qll begins to drop.Also, this decrease in the collector current of the transistor Qll causes a voltage drop across the resistor R1t. As a result, the base potential of transistor Q12 becomes high.Because of the positive feedback caused by this procedure, transistor Q1.2 is completely turned on, transistor Qll is completely turned off, and the oscillation mode is reversed.

This circuit repeats oscillation with this as a half cycle, but when the control current Ic of the excavation frequency is changed, the transistor Ql
The collector current of the ON (ON) of Q12 changes, and the voltage drop of the resistor due to this current prevents the change of the oscillation frequency.To prevent this, diode D
11j) A variable current source with a switch based on rz, a transistor Q1s, and a resistance ratio of 15 is provided.

After that, transistor Qll is turned on again, and Ql2 is turned off.
'Think about when you're doing it. At this time, transistor Q12
In order for transistor Q12 to turn on, the emitter' disturbance must be equal to the sum of the 17L pressure drop of the resistance ratio 11 and the base-emitter voltage of transistor Q12.
At this time, the emitter potential of transistor Qll has a resistance ratio of 1
2 and the base-emitter voltage of transistor Q1+. Therefore, when the oscillation mode is inverted, the one-pot difference between the two ends of the capacitor C is equal to the resistor 1 (+
1 s JLt 20'1 Equal to the difference in pressure drop. In order to control the oscillation frequency, it is necessary to make the difference in voltage drop across this resistor ILtt, approximately 12, always equal when changing the charging/discharging current of the capacitor JkC. Therefore, the resistance ratio is set to 11. The same voltage drop as the voltage drop due to the generated control current is caused to occur in the resistor R,12. For this reason, resistors Rxx and R+x2 are of the same size, and transistors pQx3 . The collector current of Qt4 is always the same magnitude, and the collector current of transistor Q15 is always the same magnitude as that of transistors Q13. Assume that the current is twice the collector current of Q14. If you do this, the transistor Q is now turned on.
Since the base potential is higher than the base potential of the transistor Q12, the diode Dll is turned on, and the collector current of the transistor Q15 flows through the resistors R and x2. The potential difference between the bases of the transistors Qll and Q12 ultimately corresponds to the voltage drop across the resistor Rtt due to the currents of the constant current sources 811 and 812. Therefore, the potential difference between both ends of the capacitor C for reversing the oscillation mode is always a constant value. In this operation, transistor Q1t is 0FFLQ1
The same is true when 2 is ON.

In this way, the oscillator according to the present invention does not require the switches of transistors Q5 to Q8 that were necessary in the conventional oscillator shown in FIG. 2, and the type of voltage-current converter for controlling the oscillation frequency is also different. , it can operate with a lower power supply voltage and the number of elements constituting the circuit can be reduced. That is, by changing the control current here, the resistance ratio is 21.

Since the voltage drop of each R゛22 changes, a margin for the voltage range is required, but this value can be reduced by setting the resistance value and current value, so the voltage is lower than that of the conventional circuit. It is possible to operate at

Further, if the output is taken out differentially from both ends of the capacitor C, for example, no influence will be exerted.

〔Effect of the invention〕

According to the circuit as described above, the voltage required as the power supply voltage VB can be reduced, and the number of elements constituting the circuit can be reduced, so that the configuration can be simplified.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a voltage controlled oscillator according to the present invention, and FIG. 2 is a circuit diagram of a conventional voltage controlled oscillator. QllS-Q15...Transistor, Vf...
Variable voltage source/RJllS-R15...Resistance, Dll, DI2 Diode, Sll, 8
12...Reference 1 current source, C...Capacitor, VB...Reference voltage source. Agent Patent Attorney Noriyuki Chika Yudo Hiroshi Uji・-IJ Midenko Figure 1

Claims (1)

[Claims] a first, in which the collector of one is interconnected to the base of the other;
a second transistor, first and second resistors that respectively connect the collectors of the first and second transistors to a power supply, and a capacitor that capacitively couples the emitters of the first and second transistors to each other; first and second diodes whose cathodes are connected to each other and whose anodes are connected to the bases of the first and second transistors, respectively, and to the emitters of the first and second transistors, each of which is equal to the first and second variable current sources supplying current; and the first and second variable current sources connected to the cathodes of the first and second diodes.
and a third variable current source that supplies a current corresponding to the sum of the currents supplied by the variable current sources, and the first to third variable current sources are controlled by a control voltage to vary the oscillation frequency. A voltage controlled oscillator characterized by: