JPH043686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a stabilizing bias circuit used in amplifier circuits and the like constituting radio receivers, stereo equipment, and other equipment.

Configuration of the conventional example and its problems FIG. 1 is an electrical wiring diagram of an amplifier circuit used in the conventional example. In Fig. 1, the amplifier 3 has a positive input terminal (+), a negative input terminal (-), and an output terminal 6, and generally the DC voltage at the output terminal 6 is the power supply voltage (V _CC ) of one side and the power supply voltage of the other side. It is constructed so that a signal with a large amplitude can be extracted when the voltage is between the voltage (earth).
That is, the resistor R ₁ connected to the positive input terminal (+)
and resistor R ₂ are set almost the same value, and the bias of the positive input terminal (+) is set to a voltage approximately halfway between one power supply voltage (V _CC ) and the other power supply voltage (earth). Further, negative feedback is applied to the negative input terminal from output terminal 6 via resistor R ₃ , and output terminal 6
The voltage is set to be approximately halfway between one power supply voltage (V _CC ) and the other power supply voltage (earth).

FIG. 2 shows the amplifier 3 shown in FIG. 1 in more detail, and generally the amplifier 3 is a second
As shown in the figure, a differential amplifier consisting of two transistors 9 and 10 is often used. In FIG. 3, the base of transistor 9 is the positive input terminal,
The base of the transistor 10 is a negative input terminal,
The base of transistor 9, that is, the positive input terminal, is biased by resistors R ₁ and R ₂ to a voltage approximately halfway between one power supply voltage (V _CC ) and the other power supply voltage (earth). Therefore, if the contact potential difference V _BG between the base and emitter of transistors 9 and 10 is approximately 0.7V, the emitter voltage of transistors 9 and 10 is approximately 0.7V lower than the base of transistor 9. This means it is working. Therefore, when one power supply voltage (V _CC ) becomes 1.4V or less, the base voltage of transistor 9 becomes 0.7V or less, and transistor 9,
The voltage between the emitter and the base of 10 becomes 0.7V or less, and current no longer flows through resistor 11, making it inoperable.

In the amplifier circuit shown in FIG. 2, when the power supply voltage changes, the current flowing through the resistors 11 and 13 changes, and the current flowing through the transistors 9 and 10 changes accordingly, so the gain of the entire amplifier circuit changes. It turns out. In FIG. 3, transistors 20 and 22 are separately provided, and the transistors 20 and 2 are separately provided.
The base of 2 is biased to a constant voltage to operate as a constant current circuit, and even when the power supply voltage changes, the current flowing through transistors 9 and 10 changes less, and the gain change as a whole is reduced. . That is, in this case, a constant voltage bias circuit 40 as shown in the dotted line has conventionally been used.

Here, the constant voltage bias circuit 40, which has been widely used in the past, will be explained.

When a voltage is applied to one power supply terminal V _CC , current flows through the starting resistor 30 via the diode 31 and current also flows through the transistor 32 . The transistor 32 and the diode 31 operate as a current mirror circuit, and the current flowing to the collector of the transistor 32 flows to the diodes 26 and 27. When current flows through the diodes 26 and 27, a voltage appears across the diodes and is applied to the base of the transistor 29. Therefore, current also flows through the transistor 29, and the current flowing through the diode 31 increases and stabilizes at the current value determined by the resistor 28. In other words, the voltage across the diodes 26 and 27 is the contact potential difference between the base and emitter of the transistor 29.
It becomes stable when it becomes equal to the sum of V _BE and the voltage drop due to the resistor 28. For example, if the value of resistor 28 is 1KΩ, diodes 26, 2
7 and the base-emitter voltage _VBE of transistor 29 are almost the same, 0.7V, so the voltage at the emitter of transistor 29 becomes 0.7V, and 700 μA flows through resistor 28, making it stable. The voltage at the base of transistor 29, that is, at point A, is always _{approximately}
It becomes 1.4V. Therefore, this voltage is applied to the resistor 24,
If the voltage at point B is set to approximately 1.0V, this stabilizing bias circuit 40 will have a power supply voltage of approximately 1.0V.
It will work satisfactorily even if the voltage drops to around 1.5V. As mentioned earlier, the amplifier will operate even if the power supply voltage drops to nearly 1.4V, so if you configure it as shown in Figure 3, the power supply voltage can be reduced.
Although it can be operated satisfactorily even when the voltage drops to 1.5V, there is a problem in that it does not operate at all below that level.

Purpose of the Invention The present invention eliminates the above-mentioned conventional drawbacks, and provides an excellent stabilizing bias circuit that has a simple configuration and operates sufficiently stably even at a lower power supply voltage than the conventional stabilizing bias circuit. The porpose is to do.

Structure of the Invention The present invention includes a first element consisting of one diode or one diode-connected transistor;
a second element consisting of a plurality of transistors or a transistor having a contact potential difference lower than the contact potential difference of the first element; a third element consisting of a current mirror diode or a diode-connected transistor; and a fourth element consisting of a transistor. Prepare an element, connect the base-emitter of the transistor constituting the second element in parallel with the first element and the first resistor, and connect the third element to the collector of the transistor constituting the second element. By connecting the base and emitter of the transistor constituting the fourth element in parallel with the third element, and connecting the collector of the transistor constituting the fourth element to the first element, it is possible to maintain voltages that are sufficient even for low power supply voltages. This is to obtain an excellent stabilizing bias circuit that operates in a consistent manner.

DESCRIPTION OF THE EMBODIMENTS FIG. 4 shows the basic circuit configuration of an amplifier circuit suitable for using the stabilizing bias circuit of the present invention. In Figure 4, the value of resistor R ₁ is, for example,
2KΩ, the value of resistor R ₂ is 8KΩ, and the power supply voltage V _CC is 1V, then there will be a voltage drop of 0.2V across resistor R ₁ . Therefore, the base of transistor 9 becomes 0.8V,
The base of transistor 10 also needs to be at 0.8V. And the output terminal 6 is the power supply voltage
A large output voltage can be obtained when the voltage is 1/2 of V _CC , so the value of resistor R ₄ is set to 2KΩ, and the value of resistor R ₃ for negative feedback is set to 3KΩ. In this way, the bases of transistors 9 and 10 are both
It becomes 0.8V.

In other words, if the values of the resistors R ₁ to _{R 4} are set to R ₁ /R ₁ +R ₂ =R ₄ /R ₃ +R ₄ × 1/2, the output terminal 6 will have a voltage that is approximately 1/2 of the power supply voltage V _CC . Therefore, a large signal can be output to the output terminal 6.

In this case, the emitter voltage of transistors 9 and 10 is approximately 0.1V, and
A sufficient current flows through 10 for operation.
Note that the transistors 9 and 10 are transistors that operate if the voltage between the collector and emitter is 0.1V or more. In this circuit, the contact potential difference between the base and emitter of diode 8 and transistor 12 is approximately
Since the voltage is 0.7V, the current between the collector and emitter of transistors 9 and 10 is approximately 0.2V, and the transistors can operate satisfactorily. In this way, in the amplifier circuit shown in Figure 4, the voltage drop due to resistors R ₁ and R ₄ is reduced to 0.2V.
Therefore, it can operate satisfactorily even when the power supply voltage V _CC is 1.0V. If the voltage drop across resistors R ₁ and R ₄ is 0.7V or less, it will operate even if the power supply voltage V _CC is 1.4V or less. In other words, the voltage drop across resistors R ₁ and R ₄ is set below the contact current V _BE between the base and emitter of the transistor, and the relationship R ₁ /R ₁ +R ₂ =R ₄ /R ₃ +R ₄ × 1/2 is established. If this holds true, even if the power supply voltage changes, the voltage drops across resistors R ₁ and R ₄ will be almost the same, so the DC voltage at output terminal 6 will be approximately 1/2 of the power supply voltage V _CC . It is possible to extract a large output signal.

By the way, in the amplifier circuit shown in Figure 4, the power supply voltage
Although it operates satisfactorily even when V _CC drops to about 1.0V, the current flowing through the resistors 11 and 13 changes with changes in the power supply voltage V _CC , so the gain of the amplifier circuit as a whole changes. Therefore, in order to reduce this, transistors 51 and 52 are used instead of resistors 11 and 13 as shown in FIG.
It is necessary to provide a stabilized bias to 1,52.

The present invention is a stabilizing bias circuit for obtaining such a stabilized bias voltage, and one embodiment thereof will be described below with reference to FIG. 5. In FIG. 5, 61 is a starting resistor, and a resistor with relatively high resistance is used. When the power supply voltage V _CC is applied, current flows through the diode 62 via the starting resistor 61 and current also flows through the transistor 63 . The current flowing to the collector of the transistor 63 flows to the diode 67 constituting the current mirror circuit, and the transistors 68 and 69 become operational. Then, the current flowing through the collector of the transistor 68 flows through the diode 70, and the voltage across the diode 70 is applied to the bases of the transistors 64 and 65, so that current also flows through the transistors 64 and 65, and the entire device becomes operational. Note that the diodes 8, 67, 70, 71, and 62 may be diode-connected transistors.

In the above example, the diode 70 now has 200μA
When a current is applied, the contact potential difference between both ends is the sixth
Assume that the voltage is approximately 0.7V as shown in Figure a. Since the transistors 64 and 65 operate as a current mirror circuit with the diode 70, a current of 100 μA, which is half of the current flowing through the diode 70, flows through each transistor 64 and 65. transistor 64,
When the current flowing through 65 is 100μA, transistor 6
Contact potential difference between base and emitter of 4,65 V _BE
For example, if the voltage becomes about 0.65V as shown in FIG. There must be.

(Actually, the current flowing through the transistor 63 also flows through the resistor 66, but its value is very small and can be ignored.) Therefore, the value of the resistor is
It is necessary to set 0.05 (V)/200×10 ^-6 (A) = 250 (Ω), and by doing so, 200 μA will flow through the circuit and stable operation will be performed.

In this way, according to the above embodiment, the transistor 6
Between the emitters and collectors of 8, 69, 65, and 64
Coupled with the ability to operate even when the voltage drops to 0.1 to 0.2V, the voltage across the diodes 67 and 70 _{, VBE} , is approximately 0.7V.
If this is the case, it will operate stably even if the power supply voltage V _CC drops to 0.8 to 0.9V. Therefore, in this case, the collector of transistor 69 also has approximately
A current of 200μA will flow through diode 7.
A current of 200 .mu.A flows through transistors 51 and 52, which operate as a current mirror circuit between the transistors 1 and 1, and as a result, the entire amplifier circuit can be operated in a stable state without loss of gain even at low power supply voltages.

In the embodiment, the transistor 69 and the diode 71 may be omitted, and the bases of the transistors 51 and 52 may be directly connected to the bases of the transistors 64 and 65. However, in this case, the power supply voltage
When V _CC drops to 0.8 to 0.9 V, a portion of the current flowing through diode 70 simultaneously flows to the bases of transistors 51 and 52, so that the stability may deteriorate slightly. In other words, when the voltage between the collector and emitter of the transistor decreases, the current amplification factor h _FE of the transistor decreases, the base current increases, and the current in the stabilizing loop flows outside, reducing the overall stability. This will result in a decline.

Next, I will explain about the starting circuit, and for the starting resistor 61, it is best to choose one with high resistance.
Suppose it is 100KΩ. In this case the supply voltage
Assuming that V _CC is 1.0V, a current of 1-0.7/100×10 ³ =3 μA flows through the resistor 61, and this same current flows through the diode 62 as well.

As described above, according to the above embodiment, when the stabilizing bias circuit is operating, there is a voltage drop of 0.05V across the resistor 66. Since a current of 3 μA is flowing through the diode 62, the contact potential difference at this time is the 6th
As shown in Figure c, if the voltage is 0.5V, the voltage between the base and emitter of transistor 63 is 0.5-
0.05=0.45V, and since the voltage between the base and emitter of the transistor 63 is low, for example, only a current of 0.1 μA flows through the transistor 63. If the emitter of transistor 63 were directly grounded, the same current of 3 μA as the current flowing through resistor 61 would flow through transistor 63. Also, if the power supply voltage V _CC becomes 3V, a current of 3-0.7/100 x 103 = 23μA flows through the resistor 61 and the transistor 6
If the emitter of transistor 3 is directly grounded, then transistor 63 is connected to the collector of transistors 64 and 65.
There is a problem in that the collector currents of transistors 51 and 52 flow simultaneously, resulting in a large change in the current in the stabilizing bias circuit and a large change in the currents in the transistors 51 and 52. However, in this embodiment, transistor 6
The emitter of 3 is connected to the resistor 66 and the transistor 64,6
Since it is connected to the connection point of the emitter of transistor 63, even if the power supply voltage V _CC becomes 3V, the collector current of transistor 63 is only about 0.8 μA, which is negligible with the 200 μA current of the stabilizing bias circuit, and the power supply voltage Its stability is hardly affected by fluctuations in V _CC .

Furthermore, in the above embodiment, the voltage drop across the resistor 66 connected to the emitter of the transistor 63 is the power supply V _CC
Since it is small when turned on, a large current initially flows through the transistor 63, and once the circuit operates and stabilizes, the voltage drop across the resistor 66 increases, reducing the current flowing through the transistor 63.

In addition, in the embodiment, two transistors 64 and 65
Although they are used by connecting them in parallel, it is also possible to replace them with a single transistor. However, in this case, it is necessary to make the contact potential difference of the transistor lower than the contact potential difference of the diode 70.

Effects of the Invention As explained above, the stabilizing bias circuit of the present invention can operate stably even at low power supply voltages with a simple configuration, and is extremely advantageous in practice.

[Brief explanation of drawings]

Figures 1 to 3 are electrical wiring diagrams of commonly used amplifier circuits and their stabilizing bias circuits, and Figure 4 is the basic configuration of an amplifier circuit to which the stabilizing bias circuit of the present invention can be applied. 5 is an electrical connection diagram of an embodiment of the stabilizing bias circuit of the present invention and its application circuit, and FIG. 6 is a voltage-current characteristic diagram for explaining the main parts thereof. 1... Signal input terminal, 2, 5... Capacitor,
4, 61, 66, R ₁ ~ R ₄ ... Resistor, 6 ... Output terminal, 7, 9, 10, 12, 51, 52, 63,
64, 65, 68, 69...transistor, 8,
62, 67, 70, 71...diode.

Claims (1)

[Claims] 1 A first element consisting of a diode or a diode-connected transistor, a second element consisting of a plurality of transistors or a transistor having a contact potential difference lower than the contact potential difference between the base and emitter of the first element, and a current mirror element. A third element consisting of a diode or a diode-connected transistor, and a fourth element consisting of a transistor, the base of the transistor constituting the second element being connected to one of the first elements, and the emitter of the transistor constituting the second element being connected to one of the first elements. One of the third elements and the base of the transistor of the fourth element are connected to one of the resistors, and the collector of the transistor forming the second element is connected to the collector of the transistor forming the fourth element. One of the first elements is connected to the base of the transistor of the second element, and the collector and emitter of a separately provided fifth transistor are respectively connected to the collector and emitter of the transistor constituting the second element. A stabilizing bias circuit characterized in that the base of the transistor is connected to a connection point between one of a sixth element consisting of a separately provided diode or a diode-connected transistor and a starting resistor.