JPH02202104A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To realize an oscillatory operation stable more than ever by providing a DC negative feedback circuit. CONSTITUTION:The oscillation circuit is comprised including an oscillation circuit main body 1, a high impedance bias circuit 2, and the DC negative feedback circuit 3. Here, a differential amplifier including a pair of npn transistors 10 and 11, a constant current source 13, and pnp transistors 8 and 9 which form a current mirror load circuit is comprised. And DC feedback is performed by the DC negative feedback circuit 3 being positively fed back by a capacitor 12 and including npn transistors 21 and 22, a pnp transistor 23, a constant current source 26, a resistor 24, and a capacitor 25. Thereby, the differential pair of transistors 10 and 11 can be operated actively while no offset current exceeds the current of the constant current source 13, then, stable oscillation can be maintained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an oscillation circuit, and in particular to a resonance circuit of a ceramic resonator, etc. as a voltage controlled oscillator (VCO) of a phase-locked loop (PLL) in an integrated circuit for FM stereo demodulation. This invention relates to a one-terminal type oscillation circuit using a child.

[Conventional technology]

FIG. 2 shows a circuit diagram of a conventional one-terminal oscillation circuit. In FIG. 2, an l-terminal type oscillation circuit body 30 using a ceramic resonator X is used.

Here, the bias circuit 31 for applying an operating bias to the oscillation circuit main body 30 includes transistors 32 . to 3
Consists of 9. Further, the reactance circuit '40 is a circuit for finely adjusting the oscillation frequency of the oscillation circuit main body 30.

The oscillation circuit main body 30 oscillates at the parallel resonance frequency of the resonator
pn) transistor 43, a pnp transistor 44, 45 forming a current mirror type load, two diodes 46, 47, and one feedback capacitor 48. Here, the ceramic resonator X does not have a bypass effect like the LC parallel element of the LC oscillation circuit, and the positive feedback necessary for oscillation is performed by the feedback capacitor 48.

[Problem to be solved by the invention]

In order to maintain stable oscillation operation in the oscillation circuit main body 30 using the ceramic oscillator X in FIG. It won't happen.

In order to realize this, the following two items can be considered.

(2) The bias circuits for the transistors 41 and 42 are configured completely symmetrically without applying negative DC feedback to the amplification transistors 41 and 42.

(2) A DC negative feedback circuit is provided to maintain the active operation of the amplifying transistors 41 and 42.

Although the configuration (2) is adopted in the bias circuit 31 of FIG. 2, it is difficult to obtain stable operating conditions because of manufacturing variations in each element within the integrated circuit. That is,
In FIG. 2, the currents of the bias current supply transistors 36 and 37 in the bias circuit 31 are equal, and the hPI of the amplification/constant current transistors 41, 42, and 43 in the oscillation circuit 30 are the same. is a condition for sustaining stable oscillation, but it is difficult to maintain this condition due to manufacturing variations, leading to a decrease in yield.

[Means to solve the problem]

The configuration of the oscillation circuit of the present invention is such that a bias circuit applies positive feedback to a differential amplifier circuit via a capacitor, and a DC negative feedback circuit is added to the differential amplifier circuit to ensure stable oscillation. It is characterized by

〔Example〕

Next, the present invention will be explained with reference to the drawings. ◎ Fig. 1 is a circuit diagram showing an oscillation circuit according to an embodiment of the present invention. In FIG. 1, an oscillation circuit according to an embodiment of the present invention has a first transistor 10 and a second transistor 11 having a first polarity, whose emitters are commonly connected to a first constant current source 13, and whose emitters are connected in common to a first constant current source 13. Transistor 11017) The collector and base of a third transistor 8 with a second polarity opposite to that of the first transistor 10 are connected to the base of a fourth transistor 9 with @2 polarity. 4 transistor 9
The emitter of the fourth transistor 9 is connected to the first power supply, the collector of the fourth transistor 9 is connected to the collector of the second transistor 11, and the collector of the second transistor 11 is connected to the first power supply.
The collector of the fifth transistor 21 is connected to the base of the fifth transistor 21 of the first polarity. The emitter of the sixth transistor 22 is connected to the emitter of the seventh transistor 23 of the second polarity, and the base and collector of the seventh transistor 23 are commonly connected to the second constant current source 26. has been done. seventh transistor 23
The base and collector of are further connected to the base of the second transistor 11 via a first resistor 24, and the base of the second transistor 11 is connected to a first capacitor 25.
The emitter of the eighth transistor 14 of the second polarity is connected to the first power supply, and the emitter of the eighth transistor 14 of the second polarity is connected to the second power supply through the
The base of the transistor 14 of pJc9 is connected to the base of the ninth transistor I5 of the first polarity, the collector of the transistor 15 of pJc9 is connected to the first power supply, and the collector of the eighth transistor 14 is connected to the base of the ninth transistor I5 of the first polarity. The collector of the transistor 14 of [88] is connected to the emitter of the first O transistor 16 of the second polarity, and the collector of the first O transistor 16 is connected to the second power supply The base of the tenth transistor 16 is connected to the base of the eleventh transistor 17 of polarity XtrilXl, and the base of the tenth transistor 16 is connected to the second transistor 1 through the second capacitor t12.
The collector of the eleventh transistor 17 is connected to the emitter of the ninth transistor 15, the emitter of the eleventh transistor 17 is connected to the third constant current source 18, and the collector of the eleventh transistor 17 is connected to the third constant current source 18. transistor 1
The emitter of 7 is connected to the base of the first transistor 10 via the third resistor 19, and the emitter of the second transistor 11
The collector of is used as an output terminal 7, a resonator X is connected between the output terminal 7 and the second power source, and the output terminal 7 is further connected to the reactance circuit 4.

That is, the oscillation circuit of this embodiment includes: 1 degree oscillation circuit body, 2.degree. high impedance bias circuit. including a DC negative feedback circuit 3;
configured.

Here, a pair of npn transistors 10, 11.degree. constant current source 13. prip as a current mirror load circuit
A differential amplifier including transistors 8 and 9 is configured, and a capacitance of 1
2, positive feedback is provided by npn transistors 21,
22. pnp transistor 23° constant current source 26. Resistance 24. A DC negative feedback circuit 3 including a capacitor 25 provides negative DC feedback. Zarani s pn
p)'Run raster 14.16. npn) transistors 15, 17. and constant current source 18. Resistance 5, 19. A high impedance bias circuit 2 including a constant voltage source 6 is provided with positive feedback to the transistor IOK via a capacitor 12, and negative feedback is provided from the collector terminal of the transistor 11 to the base terminal of the transistor 11. , through the emitter follower of the DC negative feedback circuit 3.

Due to these K, the output impedance of the collector terminal of the transistor 11 is kept high, and the Q of the ceramic resonator Therefore, most of the AC component (oscillation frequency component) is bypassed, and only the DC component is negatively fed back.

Then, when the current flowing through the reactance circuit 4 is zero,
Transistors 10 and 11a of the differential pair operate stably in a balanced state (assuming that constant current 18° and constant current 26 are equal), the base currents of transistors 10 and 11 are equal, and between the base and emitter of transistor 17 Voltage V
IK and VBIC of transistor 2 become equal, and transistor 16. Vi+z of the transistor 23 becomes equal. Therefore, the output terminal 7 of the oscillation circuit body 1 is fixed at a stable potential that is higher than the DC voltage source 6 by VBK of the transistor 22, and the reference voltage of the output terminal 7 is determined by the potential of the DC voltage source 6. Potential can be easily set.

Also, reactance circuit 4! 'c If there is an offset current, for example, the offset current causes the transistor 11 to
The output DC voltage at the collector terminal of the transistor 10 decreases, the base potential of the transistor 11 fed back by the DC negative feedback circuit 3 also decreases, and the collector current of the transistor 10 increases.
The currents of transistors 8 and 9, which are current mirror load circuits, increase. As a result, the differential pair of transistors io,
The difference between the collector currents ii and ii becomes stable in a state where it is equal to the offset current.

In other words, offset 1! As long as the current does not become larger than the current of the constant current source 13, the transistors 10.1 of the differential pair
1 can operate actively and maintain stable oscillation.

〔Effect of the invention〕

As described above, by providing a DC negative feedback circuit, the present invention can obtain a stable DC operating voltage even with variations in circuit elements, thereby enabling stable oscillation operation and bypassing the oscillation frequency. Since it has a high impedance bias circuit and a high impedance bias circuit, it has the effect of enabling more stable oscillation operation.

FIG. 1 is a circuit diagram showing a one-terminal oscillation circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional one-terminal oscillation circuit.

1... Oscillation circuit main body, 2... High impedance bias circuit, 3... DC negative feedback circuit, 4,4゜... Reactor/s circuit, 5,19,
24.49...Resistance, 6...DC voltage source, 7,5o...Output terminal, 8, 9.10.1
1.14.15.16.17.21゜22.23.32
~39.41~45...T-)/Jista, 12
．． 48 ...Feedback capacitance, 13, 18.26°°
... Constant current source, 25 ... Bypass capacity, 4
6.47...Diode.

Agent: Patent Attorney Susumu Uchihara

[Brief explanation of the drawing]

No. ”

Claims (1)

[Claims] An oscillation circuit characterized in that a bias circuit applies positive feedback to a differential amplifier circuit via a capacitor, and a DC negative feedback circuit is added to the differential amplifier circuit to ensure stable oscillation.