JPS606128B2 - oscillation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oscillation circuit using a pair of differentially connected transistors.

Figure 1 shows a bias circuit for a conventional pen amplifier. Transistors 3 and 4 and resistor 7 constitute a differential amplifier, and the output can be obtained from both or one of load resistors 5 and 6. The resistors 1, 2 and 8, 9 are bias resistors and are usually set so that the base voltages of both transistors 3, 4 are equal in terms of direct current.

The signal is applied directly to the bases of the transistors 3 and 4, or in series between one of the resistors 1, 2, 8, and 9 and the reference potential. The signal to be amplified is connected to the feedback voltage as the other input, or a bypass capacitor is sometimes connected.Therefore, the impedance of the signal source bias circuit etc. seen from the base of the differential amplifier is usually The input impedance of the signal input terminal is influenced by the input bias resistor and therefore the resistors 1, 2 or 8, 9 It becomes a parallel resistance of 1, 2, 8, and 9, and it is difficult to obtain a high value, especially when there is a restriction on the upper limit of the resistance value of an integrated circuit. 2 or 8 and 9, the signal voltage is divided by the resistors 1 and 2 or 8 and 9 and is attenuated, which may be inconvenient.

The present application relates to a bias circuit used in an electric circuit such as a multiplier configured in a plug-in type, which solves the drawbacks of the prior art.

Next, the principle embodiment of the present invention will be explained with reference to FIG. 2. Transistors 23, 24 and resistors 25, 26, 27 constitute a differential amplifier as in FIG. 1.

A current flows through the diode 301 through the resistors 28 and 29, and the base of the transistor 22 is connected to the anode side of the diode 30, forming a current mirror. The collector voltage of the transistor 22 is between the collector current of the transistor 22 and the value of the resistor 21, that is, it depends on the current value of the diode 30. If the base-to-emitter voltage characteristics of the diode 30 and the transistor 22 match, the currents of both will be 1:1, and if the values of the resistors 21 and 28 are the same, the voltages across the resistors 21 and 28 will be the same, and this The voltage may be the base bias of the differential multiplier. The current ratio can also be adjusted to n:1 by inserting a resistor between the emitter of the transistor 22 and the cathode of the diode 30. Furthermore, if the power supply voltage is significantly higher than VB8 of the transistor 22, the diode 30 can be replaced with a resistor. The current flowing through the resistor 28 and the resistor 21 may be set, and in these cases and the diode 3
If the area ratio of the cathode of 0 and the emitter of the transistor 22 is selected to be n31, the ratio of the resistors 21 and 28 is 1 and n; The input terminal of the intensifier can be biased.In this case, the impedance seen from the base of the transistor 23 to the bias circuit is only the resistor 21, which can be significantly increased compared to the conventional technology even if the same resistance value is used. The signal source can be connected in series to either the bases of the transistors 23, 24 or the resistors 21P to 28, or can be connected in series with the diode 3M or to the emitter side of the transistor 22. Furthermore, the base bias circuit of the transistor 23 When a signal source is connected to the side, the base of the transistor 24 is not affected.

In this case, if a signal source is inserted in series with one end of the power supply and the resistor 21', a constant current is flowing through the resistor 21 by the transistor 22, so there is no loss of signal voltage even if the DC level simply changes. If a signal source is connected to the base bias circuit side of the transistor 24 that can be applied to the base of the transistor 23, a signal of the opposite phase will be applied to the base of the transistor 23 via the transistor 22. "The impedance of resistor 29 is
If it is sufficiently small compared to 8, signals with an amplitude ratio of approximately 1:1 and opposite phases will be applied to the bases of transistors 23 and 24, and the voltage gain as a differential amplifier will be as shown in Fig. 1. It is also possible to double the number in the case of such a configuration. Also, even when the power supply voltage fluctuates, the current flowing through the diode 30 is determined by the resistors 28 and 29, and the collector current of the transistor 22 follows in proportion to this diode current.
The base biases of the transistors 23 and 24 fluctuate in a balanced state, causing no problem.

Further, if the diode 30 and the transistor 22 are thermally balanced, the collector currents of the diode 30 and the transistor 22 are also thermally balanced, and the bias of the differential amplifier is balanced.

FIG. 3 is a circuit diagram of an oscillation circuit showing an embodiment of the present invention, in which an output generated in a resonant load connected to the collector of a transistor 43 is connected to a resistor 44 through a transistor 45 at a constant current (generated in a resonant load). A constant current (determined by the power supply voltage, which is not affected by the output voltage) is level-shifted and applied to the base of the transistor 42, and a sine wave oscillation circuit is constructed by positive feedback.

In this case, conventionally, the voltage from the resonant circuit was fed back to the base of the transistor 42 using a capacitor, but since this can be done with a resistor, integration into an integrated circuit becomes easier.

As described above, the present invention can be widely applied to oscillation circuit feedback amplifiers, etc., and in particular, if it is applied to negative feedback amplifiers and a DC negative feedback loop is configured including the bias circuit according to the present invention,
The DC stability of the multiplier increases dramatically.

Therefore, the scope of application of the present application is extremely wide, and it can be easily integrated into an integrated circuit. Brief Description of the Drawings FIG. 1 is a circuit diagram showing an example of a slave differential amplifier.

FIG. 2 is a circuit diagram showing a basic embodiment of the present application. FIG. 3 is a circuit diagram showing an embodiment of the present invention. FIG. 3 is a circuit diagram in which the invention of the present application is applied to an oscillation circuit. In the figure 1, 2, 5, 6, 7, 8, 9, 21, 25, 2
6, 27, 28, 29, 31, 36, 35, 37, 38
, 39, Turtle 4 ri 46, 49... Resistance, 3, 4, 22
, 23, 24, 32, 33, 34, 42, 43, 45...
...Transistor, 30, 41, 51...Diode, 4
0,50...constant voltage element, 47...capacitor, 48...
···coil.

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Claims (1)

[Claims] 1 first and second transistors connected in a differential manner, circuit means for supplying a base bias voltage to the first transistor, and a circuit means for receiving a voltage obtained from a part of the circuit means between the base and emitter. The third component constituting the constant current source
a resonant circuit connected between a transistor, a collector of the first transistor and a power supply; one end connected to the collector of the first transistor and the other end connected to the base of the second transistor and the collector of the third transistor; An oscillation circuit comprising a feedback resistor connected to the oscillator circuit.