JPS5983408A - Amplifying circuit - Google Patents

Abstract

PURPOSE:To ensure the satisfactory working of an amplifying circuit even with a level less than the contact potential difference VBE, by securing a specific relation with plural resistance values connected to positive and negative input terminals respectively for an amplifier containing positive and negative input terminals. CONSTITUTION:Transistors TR9 and 10 are used to form an amplifier containing positive and negative input terminals. A voltage dividing circuit consisting of resistances R1 and R2 is connected to the base of the TR9 which functions as a positive input terminal. A circuit consisting of resistances R3 and R4 is connected to the base of the TR10 which functions as a negative terminal. A specific relation is set between those resistances, that is, (R1/R1+R2)XVCC= (R4/R3+R4)XVCC/2. In such a constitution, an amplifying circuit can work even with the voltage with which the bias voltage of the positive and negative input terminals of the amplifier is set lower than the contact potential difference VBE of the TR. Thus, a malfunction is prevented in case the power supply voltage is extremely reduced down.

Description

[Detailed description of the invention] Industrial applications The present invention is a radio receiver and a stereo system! , Part 2・-5 Concerning amplifier circuits used in other applications.

Configuration of conventional example and its problems Figure 1 shows a conventional amplifier circuit.
7g3 is the positive input terminal (→ and negative input terminal (→ and output terminal 6)
It is generally configured so that a signal with a large amplitude can be extracted by setting the bias voltage of the output terminal 6 to an intermediate voltage between one power supply (Vcc) and the other power supply (earth). has been done. Therefore, the resistors R1 and R2 are set to approximately the same value so that the voltage is approximately midway between the bias voltage of the positive input terminal (field), the other power supply (Vcc), and the other power supply (earth).

Then, negative feedback is applied to the negative input terminal H from the output terminal 6 through the resistor R3, and the voltage at the output terminal 6 is changed to one power supply (Vcc
) and the other power supply (ground).

FIG. 2 shows more specifically the inside of the amplifier 3 shown in FIG. 1, and as the amplifier 3, 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, and the base of transistor 10 is the negative input terminal.

And the base of I-run star 9, that is, the city input terminal E
The values of the resistors R1 and R2 are made almost the same so that r is approximately half the voltage of one power source (Vcc) and the other power source (earth). For this reason, the contact potential difference VBE between the base and emitter of the transistors 9 and 10 is approximately ○. Therefore, the emitters of transistors 9 and 10 Ichikawa are 1-
Electricity Fr lower by about 0.7V than the base of Run/Meta 9
This means that it is running on E. Therefore, one power supply (V
cc) becomes 1.4V or less, the base voltage of transistor 9 becomes 0.7V or less, and transistors 9 and 10
The emitter and base voltages of . , 7V or less, current no longer flows through the transistors 9 and 10, and the transistors 9 and 10 no longer operate.

In the conventional amplifier circuit, the power supply voltage (Vcc) is 1.4v.
The drawback is that the amplifier circuit itself no longer operates when the voltage is lower.

FIG. 3 shows another conventional example; in this case,
A signal is applied to the base of the transistor 15, and the signal is amplified by a differential amplifier consisting of a 1-transistor 17 and 18.
In addition to the base of the transistor 27 from the collector of the range metal 1, the output signal is taken out from the collector of the transistor 27. In this case, the positive input terminal is 1
- The base of transistor 15, the negative input terminal is the base of 1- transistor 18, and!・Since the base of transistor 15 is almost the same as the ground voltage, 1 - transistor 15
The emitter of and the base of transistor 17 are about 0.7V. Therefore, if the negative input terminal, which is the base of the transistor 18, is also set to approximately 0.7VK, the voltage at the output terminal 6 will be between one power supply (Vcc) and the other power supply (earth).
The voltage is approximately half of that of , and a large output signal can be extracted.

In this case, the current flowing through the negative feedback resistor 26 changes from half the power supply voltage Vcc (voltage of output 6) to 0.
．． The value is the voltage obtained by subtracting 7V (l, the base voltage of the transistor 18) and dividing it by the resistor 26 (R26), but since the base voltage of the transistor 18 is always about 0.7V even if the power supply voltage Vcc changes. The current flowing through this resistor 26 is made to flow through the 1-transistor 22.

That is, by setting the value of the resistor 24 to twice the value of the resistor 26 and connecting the diodes 26 and 23 to this, the value of the resistor 24 is doubled.
By making the current flowing through the resistor 26 and the current flowing through the resistor 26 the same, and operating the transistor 22 and the diode 23 as a current mirror circuit, the power supply voltage Vcc changes, and the current flowing through the output terminal 2
When the voltage at output terminal 6 tries to change from about 1/2 of the voltage of one power supply (Vcc), the negative feedback operation of resistor 26 is used to correct this, and the voltage at output terminal 6 is changed to 1/2 of the voltage at Vcc. I am trying to set the voltage to . Note that the resistor 4 is a resistor for setting the negative feedback 1n of the AC signal, and the capacitor 5 is an innocuous capacitor.

By the way, even in the conventional amplifier circuit shown in FIG. 3, the emitter voltage of the transistors 17 and 18 operates at 1.4V, and when the power supply voltage (Vcc) falls below 1.4V. Then, current will no longer flow through the 1-transistors 17 and 18 and they will no longer operate.

As explained above, the conventional amplifier circuit has a problem in that it does not operate at all at a low voltage of 1.4V or less.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks and provides an excellent amplifier circuit that operates satisfactorily at a lower voltage than conventional amplifier circuits.

Structure of the Invention The present invention provides an amplifier having a positive input terminal, a negative input terminal, and an output terminal, even if the bias voltage between the positive input terminal and the negative input terminal is sufficiently lower than the base-emitter contact potential difference BE of the transistor. The device is designed to operate satisfactorily, so that it can operate satisfactorily even when the power supply voltage drops significantly.

DESCRIPTION OF EMBODIMENTS FIG. 4 is an electrical wiring diagram of an embodiment of the amplifier circuit of the present invention.

In Figure 4, the value of resistor R1 is 2Ω, and the value of resistor R2 is
When the value of is set to 8Ω and the power supply voltage Vcc is set to 1V, there will be a voltage drop of about 0.2V at the resistor R1. From this, the base voltage of transistor 9 becomes O, SV, so I
・The base voltage of the transistor 10 should also be approximately o, sV.

A large output voltage can be obtained by setting the voltage at the output terminal 6 to 1/2 of the power supply voltage Vcc. Therefore, here the value i-2 of resistor R4 is Ω, and the negative feedback resistor R
When 3 is set to 3Ω, the base voltage of the 1-transistors 9 and 10 becomes approximately 0.8V.

Then, the voltage of output terminal 6 becomes power supply type 1'i':Vc
The voltage becomes approximately 1/2 of c, and a large signal can be taken out at the output terminal a6.

In this case, the emitter voltage of transistors 9 and 1Q is about 0.1V, and sufficient current flows through transistors 1 to 9 and 10 to operate. Further 1 to transistor 9, 10
The voltage between the collector and emitter is one that operates when the voltage is 0.1 V or more. In this circuit, the contact potential between the base and emitter of diode 8 and transistor 12 is approximately 0.
．． 7V, and since the voltage between the collector and emitter of the 1' transistors 9 and 1o is about 0.2V, it operates satisfactorily. Since the voltage drop across the resistors R+ and R+ is about 0.2V, the device can be operated satisfactorily even when the power supply voltage VCC is 1V.

Note that there is a voltage drop due to resistors R1 and R4. , 7V or less, it is possible to obtain an amplification word that operates even when the power supply voltage Vcc is 1.4V or less.

In other words, if the voltage drops across the resistors R+ and R4 are made to be approximately the same below the contact potential between the base and emitter of the transistor, even if the power supply voltage changes, the resistors R+ and R
Since the voltage drop caused by 4 is approximately the same, the voltage at the output terminal 6 becomes approximately an intermediate voltage between the power supply voltage Vcc and the ground, and a large output signal can be extracted.

The amplification degree of transistors 9 and 10.12 is obtained.

With this, it is not possible to obtain a large amplification degree in terms of alternating current (71.), but by grounding the base of the transistor 100 via a capacitor, a large amplification degree in terms of alternating current can be obtained.

FIG. 5 shows another embodiment in which the degree of amplification can be increased in terms of alternating current. In this case, a transistor 16 is further added to the embodiment shown in FIG. but,
Also in this circuit, the value of the resistor R1 and the resistor 4 can be set to 30Ω, and the value of the resistor R3 can be set to 3Ω.

Note that the diode 8 in FIGS. 4 and 6 may be a so-called diode-connected transistor in which the base and collector are connected to each other.

Effects of the Invention 10 As explained above, according to the present invention, it is possible to obtain an excellent amplifier circuit that operates at a low voltage 1 with a simple configuration, and is extremely advantageous in practice.

[Brief explanation of the drawing]

Figures 1 to 3 are electrical wiring diagrams of conventional amplifier circuits;
The figure is an electrical wiring diagram of one embodiment of the amplifier circuit of the present invention, and FIG. 6 is an electrical wiring diagram of another embodiment. 1... Signal input terminal, 2, 5... Capacitor, 4.11. 13, 14, 16. R1-R4・
・Self: Resistor, 7, 9, 10, 12.15: Old: Transistor, 8: Diode, 6: Output terminal. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure Vr Figure 2 rc Figure 4

Claims (1)

[Claims] a first resistor R1 having a positive input terminal, a negative input terminal, and an output terminal and connected in series between one power source and the other power source;
and a second resistor R2 are connected to the positive input terminal, and a connecting point between a third resistor R5 and a fourth resistor R4 connected in series between the output terminal and one of the power supplies is connected to the positive input terminal. connected to the negative input terminal and the first to fourth resistors R1;
．． An amplifier circuit characterized in that it can operate satisfactorily even if the voltage drop across the fourth resistors R1 and Ra is lower than the contact potential VBE between the base and emitter of the transistor.