JPS6341445B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC gain control device, and relates to a DC gain control device that allows the output control characteristics of the gain control device to be freely changed to A-type or C-type output control characteristics using a B-type variable resistor. equipment, especially
The present invention provides a DC gain control device suitable for use in IC (integrated circuit) and suitable for audio circuits of color television receivers or volume adjustment circuits of audio equipment such as radio receivers and stereo equipment.

FIG. 1 is a diagram showing characteristic curves of type A, type B, and type C volumes, where the horizontal axis represents the rotation angle (travel amount) of the volume, and the vertical axis represents the resistance value. In order to compensate for the exponential nonlinear response of the human ear, a B-type volume (linear variation type) is not used in audio amplifiers, but an A-type volume (nonlinear type) is usually used.

FIG. 2 is a diagram showing the characteristics of a commercially available type A volume.

By the way, such a non-linear A-type volume is prone to manufacturing variations, and therefore it is difficult to produce products with little variation. Therefore, it is inevitable that the characteristics will vary widely and the price will be higher than that of the linear volume, which is easier to manufacture.

The present invention has been made in view of the above circumstances, and provides a DC gain control device that is inexpensive and capable of obtaining A-type volume, C-type volume, or other characteristics by using a B-type volume that is easy to manufacture. The purpose is to

Hereinafter, the DC gain control device of the present invention will be explained in detail with reference to the drawings.

FIG. 3 is a diagram showing a circuit configuration of a DC gain control device according to an embodiment of the present invention. In the figure, 5 (circuit inside the dotted line) is a gain control circuit, 2 is an input signal terminal, C is a capacitor, 3 and 3' are output signal terminals, and 4 and 4' are gain control terminals. The gain control terminals 4 and 4' are connected to the emitters of the first and second emitter follower transistors Q ₈ and Q ₇ , respectively, and the bases of the transistors Q ₇ and Q ₈ are connected to each other, so that the base bias connected to source V ₁ ,
Each collector is connected to the _Vcc power supply. Variable resistance R ₁₆
Of the transistors Q ₁ , Q ₂ and Q ₃ , Q ₄ and Q ₅ , Q ₆ configuring the three sets of differential amplifiers, the movable terminal 1 of
The bases of each one of the transistors Q ₂ , Q ₄ , and Q ₆ are connected to each other. One end of the variable resistor _R16 is grounded and the other end is connected to the _Vcc power supply.

the other transistor of each of the three sets of differential amplifiers;
The bases of Q ₁ , Q ₃ , and Q ₅ are connected to the midpoint of resistors R ₁ and R ₂ , the midpoint of resistors R ₂ and R ₃ , and the midpoint of resistors R ₃ and R ₄ , respectively. The other end of resistor _R1 is connected to the _Vcc power supply, and the other end of resistor _R4 is grounded. The emitters of the transistors Q ₁ and Q ₂ are connected to resistors R 5 and R ₅ , respectively.
Connect to common constant current source I ₁ via R ₆ . The emitters of the transistors Q ₃ and Q ₄ are connected to resistors R 7 and R ₇ , respectively.
Connect to common constant current source I ₂ via R ₈ . The emitters of the transistors Q ₅ and Q ₆ are R 9 and R ₉ , respectively.
Connect to the common constant current source I ₃ via R ₁₀ .

By the way, the potential at the connection point between the resistors ₁ and R ₂ is Va, the potential at the connection point between the resistors R ₂ and R ₃ is V _b , the potential at the connection point between the resistors R ₃ and R ₄ is V _c , and the movable terminal of the variable resistor R ₁₆ is When the potential of 1 is changed from O to V _cc , this movable terminal 1
When the potential of _transistors Q ₅ , Q ₆ ,
The circuit section consisting of Q ₇ , Q ₈ , resistors R ₉ , R ₁₀ , and constant current source I ₃ becomes operational and output control characteristics (C characteristics)
However, _transistors Q ₃ , Q ₄ ,
The circuit section consisting of Q ₇ , Q ₈ , resistors R ₇ , R ₈ , and constant current source I ₂ becomes operational and output control characteristics (B characteristics)
However, before and after the V _a potential, transistors Q ₁ , Q ₂ ,
The circuit section consisting of Q ₇ , Q ₈ , resistors R ₅ , R ₆ , and constant current source I ₁ becomes operational and output control characteristics (A characteristics)
is obtained, and thus three different output control characteristics can be obtained.

Although it is not always specified, the emitter resistance values of the three sets of differential amplifiers are generally R ₅ =
R ₆ , R ₇ = R ₈ , R ₉ = R ₁₀ are selected.

By the way, the transistors Q ₁ , Q ₂ , Q ₃ , Q ₄ , Q ₅ , Q ₆ , Q ₁₀ , which are the constituent elements of the circuit shown in FIG.
The current amplification factor h _FE of Q ₁₁ , Q ₁₂ , Q ₁₃ is sufficiently large,
It is assumed that the base current is negligible and that the following relational expression holds true in the circuit of FIG.

I ₁ = I _c1 + I _c2 I ₂ = I _c3 + I _c4 I ₃ = I _c5 + I _c6 I ₁ + I ₂ + I ₃ = I _E7 + I _E8 = Io where I _c1 ... collector current of transistor Q ₁ ,
I _c2 ... Collector current of transistor Q ₂ , I _c3 ...
Collector current of transistor Q ₃ , I _c4 ... Collector current of transistor Q ₄ , I _c5 ... transistor
Collector current of Q ₅ , I _c6 ... Collector current of transistor Q ₆ , I _E7 ... Emitter current of transistor Q ₇ , I _E8 ... Emitter current of transistor Q ₈ Below, for example, the current of a constant current source I ₁ , I ₂ , and I ₃ are set to I ₁ :I ₂ :I ₃ =5.5:3.5:1.0, the collector currents I _{c1 to I c6 of} the transistors are as shown in Fig. 4. Based on this change, the emitter current of emitter follower transistors _Q7 and _Q8 is I _E7 ,
I _E8 exhibits current change characteristics as shown in Figure 5.
In other words, when the potential of movable terminal 1 is increased from E ₁ to E ₂ , the transistor constituting the differential amplifier
Looking at the collector currents I _c5 and I _c6 of Q _{5 and} Q 6,
I _c5 decreases and I _c6 increases. Similarly, movable terminal 1
The collector current of transistors Q ₃ and Q ₄ forming the differential amplifier when the potential of is increased from E ₂ to E ₃
Looking at I _c3 and I _c4 , I _c3 decreases and I _c4 increases. Similarly, when the potential of movable terminal 1 is increased from E ₃ to E ₄ , the transistors forming the differential amplifier
Looking at the collector currents I _c1 and I _c2 of Q ₁ and Q ₂ ,
I _c1 decreases and I _c2 increases. Note that the transistor
The differential amplifier composed of Q ₅ and Q ₆ uses transistors Q 5 and Q ₆ when the potential of movable terminal 1 is in the range of V _c (E ₁ to E ₂ ).
Gain control characteristics are provided so that Q ₆ performs completely conductive → non-conductive and non-conductive → conductive operations.

That is, the potentials of the movable terminals 1 of the other two differential amplifiers composed of transistors Q ₃ and Q ₄ and transistors Q ₁ and Q ₂ are V _B (E ₂ to _{E 3} ), respectively.
A gain control characteristic is provided so that transistors Q ₃ , Q ₄ and Q ₁ , Q ₂ are completely turned on, then turned off, and then turned off in the range of V _A (E ₃ to _{E 4} ). Based on the operation of transistors Q ₁ to _{Q 6} above, transistors Q ₇ ,
The current flowing through _Q8 changes as shown in Figure 5.

By controlling the emitter currents I _E7 and I _E8 of the emitter follower transistors Q ₇ and Q ₈ in this way, a voltage difference between the base and emitter voltage V _BE is generated, and this voltage difference is used to control the gain of gain control 5. It is led to terminals 4 and 4' and controls transistors Q ₁₀ , Q ₁₁ , Q ₁₂ , and Q ₁₃ that constitute a differential amplifier. By this control, the output characteristics of the terminal 3 become equivalent to the current control characteristics of the emitter current _IE8 shown in FIG. If the output is taken out from the terminal 3', the output characteristics will be equivalent to the current control characteristics of the emitter current I _E7 shown in FIG.

FIG. 6 is a diagram showing changes in the collector currents of transistors Q ₂ , Q ₄ , and Q ₆ when the reference bias voltages V _a , V _b , and V _c and the control characteristics of each differential amplifier are changed. The current change characteristics of the emitter currents I _E7 and I _E8 of the transistors Q ₇ and Q ₈ are as shown in FIG.

FIG. 8 is a diagram showing another embodiment of the present invention in which output characteristics similar to A type or C type are obtained using a B type volume. This DC gain control device has the same basic configuration as the circuit shown in FIG. 3 in that a differential amplifier composed of transistors Q ₁₀₅ and Q ₂₀₆ is added. In FIG. 8, a base bias source is constructed by the diode connection of transistor Q ₁₆ and resistors R ₁₇ , R ₁₈ , and R ₁₉ , and transistors Q ₇ and Q ₈ are connected to the connection point between resistors R ₁₇ and R ₁₈ . The base of the is connected. Also,
The constant current source of each differential amplifier consists of transistors Q ₁₇ to Q ₁₉ , Q ₁₁₉ , Q ₂₁₉ whose bases are connected to the connection point between the diode connection body of transistor Q ₁₆ and resistor R ₁₈
and R ₂₀ to R ₂₂ , R ₁₂₂ , and R ₂₂₂ . Furthermore, the movable terminal 1 and the transistors Q ₂ , Q ₄ ,
A first emitter follower circuit is not directly connected to the base common connection point of Q ₆ , Q ₁₀₆ , and Q ₂₁₆ and is formed of an NPN transistor Q ₂₀ and resistors R ₂₃ and R ₂₄ ;
coupled via a second emitter follower circuit formed by a PNP transistor Q ₂₁ and resistors R ₂₅ and R ₂₆ ;
Furthermore, a transistor _Q22 and a resistor are connected between the emitter follower transistors _Q7 and _Q8 and the gain control circuit.
An emitter follower circuit formed by R ₂₇ , a transistor Q ₂₃ and a resistor R ₂₈ is provided.

Under such a circuit configuration, if the control characteristics of each differential amplifier and the current ratio of the constant current source are changed, for example, the collector current of the transistor is changed as shown in FIGS. 9 and 10, the transistor The emitter current I _E8 of Q ₈ has current change characteristics as shown in FIGS. 11 and 12.

The current change characteristics obtained in this way in FIG. 11 correspond to the characteristic curve of the A-type volume shown in FIG. 1, and the current change characteristics in FIG. 12 correspond to the characteristic curve of the C-type volume shown in FIG. is approximated.
In addition, in FIGS. 9 and 10, in order to avoid crowding of the characteristic curves, only the collector current of each one transistor of the differential amplifier is shown, and the collector current of each other transistor is omitted.

As is clear from the above explanation, the gain control device of the present invention has the effect of making the output control characteristic of the gain control device A type or B type when using a B type volume (linear variation type). In addition, since the circuit elements constituting the circuit are suitable for semiconductor integrated circuits, the present invention has the advantage of being easy to integrate into semiconductor integrated circuits, and has extremely great practical value. Further, the DC gain control device of the present invention can be widely used not only for volume control circuits of audio equipment, etc., but also for gain control of other equipment.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between rotation angle or movement amount and resistance change of A type, B type and C type volume, Figure 2 is a diagram showing the characteristics of commercially available A type volume, and Figure 3 is FIG _. 4 is a circuit diagram of _a DC gain control device according to an embodiment of the present invention; FIG. The figure shows the current change characteristics of the emitter currents of transistors Q ₇ and Q _8. Figure 6 shows the reference bias voltages V _a , V _b ,
A diagram showing changes in the collector currents of transistors Q ₂ , Q ₄ , and Q ₆ when V _c and the control characteristics of the differential amplifier are changed _. , FIG _. 8 is a circuit diagram of a DC gain control device according to another embodiment of the present invention, and FIG.
Figure 0 is a diagram showing changes in the collector current of the transistor obtained by changing the control characteristics of the differential amplifier and the current ratio of the constant current source in the circuit of Figure 8, and Figures 11 and 12 are the diagrams shown in Figures 9 and 12. 10 is a diagram showing emitter current change characteristics of transistor 8 corresponding to FIG. 10. FIG. 1...Movable terminal, 2...Input terminal, 3, 3'...
...Output terminal, 4, 4'...Gain control terminal, 5...
Gain control circuit, _Q1 to _Q6 , _Q10 to _Q13 , _Q105 , _Q106 ,
Q ₂₀₅ , Q ₂₀₆ ... Differential amplifier configuration transistors,
Q ₇ , Q ₈ , Q ₂₀ ~ _{Q 23} ... Emitter follower transistor, Q ₁₄ , Q ₁₅ ... Signal input transistor,
_I1 to _I3 ...Current source, _Q16 ...Transistor diode connection body, _Q17 to _Q19 , _Q119 , _Q219 ...Transistor for current source, _R16 ...Variable resistor, _R1 to _R15 ,
R ₁₇ , R ₁₇ ′, R ₁₉ ~ R ₂₈ , R ₁₀₄ , R ₂₀₄ , R ₁₁₀ , R ₂₀₉ ,
_R210 , _R122 , _R222 ...Resistor, C...Capacitor.

Claims (1)

[Claims] 1. It has at least three transistor differential amplifiers with different gains and each has a constant current source connected to its emitter circuit, and the bases of each of the transistors constituting these differential amplifiers are commonly connected. As a DC control voltage input terminal, the bases of each other transistor are connected to different reference bias generation points, the collectors of each one transistor are connected in common, and the collectors of each other transistor are connected in common, The respective emitters of first and second emitter follower transistors, each having a collector connected to a power supply voltage terminal and a base connected to a predetermined base bias source, are connected to a common connection point between the collectors of each of the one and the other transistors. The emitters of the first and second emitter follower transistors are connected separately, and the emitters of the first and second emitter follower transistors are used as control voltage output points, and the control voltage output points are connected to gain control terminals of a current distribution type gain control circuit consisting of a differential amplifier. DC gain control device.