JPS63153905A - Gain control circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for two constant current sources and to reduce power consumption, by coupling the common emitter of sixth differential pair with fourth differential pair, and coupling the common emitter of the fourth differential pair with second differential pair. CONSTITUTION:A first gain control is performed with a control voltage applied on first differential pair and second differential pair from first control voltage input terminals 1A and 1B. A second gain control is performed with the control voltage applied on third differential pain and the fourth differential pair from second control voltage input terminals 2A, and 2B. A third gain control is performed with the control voltage applied on fifth and sixth differential pairs from third control voltage input terminals 3A and 3B. In this case, the common emitter of the sixth differential pair is coupled with the fourth differential pair, and that of the fourth differential pair with the second differential pair. In such a way, it is possible to eliminate the need for the two constant current sources and to reduce the power consumption.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a circuit that independently controls the gain of one input signal using three different external control voltages, and is particularly useful for energy saving when used in integrated circuits. This relates to a gain control circuit.

[Conventional technology]

FIG. 2 shows a conventional gain control circuit that is controlled independently by three different external control voltages. The circuit configuration and circuit operation will be explained below with reference to FIG.

The input signal VIN is a voltage-current conversion circuit, that is, a transistor Q.
The resistance R between the emitter and ground is input to the base of 13.
3 is converted into current. Here, VIN”VO+Δ
■If transistor Q1. The collector current 11 of is V(lVIE+Δ■R.

becomes. However, ■. : DC component of input signal voltage, ΔV: AC component of input signal voltage, Io: DC component of collector current, Δ■: AC component of collector current, v■: Transistor Ql! is the base-emitter voltage of

Further, the transistor QI4 and the resistor R1 constitute a first constant current source, the transistor QIS and the resistor R1 constitute a second constant current source, and the transistor QI& and the resistor R1 constitute a second constant current source.
4 constitutes a third constant current source. Generally, in the gain control output, in order to control the gain of only the AC component and keep the DC potential constant, it is necessary to
It is sufficient to set the constant current source current of 1 to a current value equal to the DC component of the input signal current, that is, the constant current source currents of the first, second, and third constant current sources should be set to a value equal to the DC component of the input signal current. The voltage source v0' and the resistor Rg are set so that
It is sufficient to set R3 and Ra.

On the other hand, transistors Q1 and C8 constitute a first differential pair, transistors Q3 and C4 constitute a second differential pair, the collectors of transistors Q and Q are connected, and the collectors of transistors Qz and C4 are connected. and connect the connection point between the bases of transistors Q2 and C3 to the control voltage input terminal lA.
, the connection point between the bases of transistors Q1 and C4 is the control voltage input terminal IB, and the input signal current is ■. +ΔI is input to the emitter of the first differential pair, and the first constant current source is connected to the emitter of the second differential pair. This circuit is a well-known balanced gain control circuit, and if the current distribution ratio of transistors Q1 and C2 is set to:1- by an arbitrary control voltage, the current distribution ratio of transistors Q4 and C3 is also changed to:l-. It becomes.

Therefore, the collector currents of transistors Q+, Qz, C3, Qa 1 el+ l C1I e3+ I
C4 is as follows.

Ic I=k (Io+ΔI) Icz=(1-k)(1G+ΔI) Ic1=(1-k)I.

1C4=kl.

Therefore, the combined current ■2 of ICI and rcl is I,=k (
To +ΔI)+(1-k)I.

=k·ΔI+1°, and it can be seen that the DC current I0 is constant and the gain is controlled to double only the AC current ΔI.

Next, transistors Qs, Q&, Qt, Q@ and the second
A constant current source constitutes a balanced gain control circuit similar to that described above, and the current distribution ratio of transistors Qs and Qt is set to m:l by arbitrary control voltages from input terminals 2A and 2B.
-m (at the same time, the current distribution ratio of transistors Q* and Qt is also m:l-m), then transistors Qs and Q
Collector current of h, Qt, Qa ■6%, lea
, Icfu, ■, and @ are as follows.

Ics=m I, =m (kΔI+Io)! . =(1
-m)It = (1-m) (kΔ■.+!.) Icy= (1-m)I.

IC,=mlO Therefore, tcs and IC? The composite current of! ,teeth,! s = T
cs+ Ict=m (kΔI+Io)+(1-m)
10 = mkΔ f+i.

Therefore, the DC current 1° is constant and only the AC current ΔI is mk
You can see that it has been doubled.

Furthermore, transistors Qq and Q+. , Q, , , Q, and a third constant current source constitute a balanced gain control circuit similar to that described above, and the transistors Q9 and Q+o are controlled by arbitrary control voltages from the input terminals 3A and 3B.

If the current distribution ratio of Q, □, and Q is n:1-n, then the transistor Q9 + qlO, Ql+, Q+z
collector voltage @I cq+ I CIO+ I c+
++ I CI2 are as follows.

I,,=n 1! =n (mkΔI+Io)Ie+a
=(I n) Is = (1-n) (mkΔI+l0)Ic++ =
(1n) I.

Te1. =nl.

Therefore, the combined current I4 of IC4 and tct+ is 14=IC
9+ ICII = n (mkΔI + IO) + (In
)I.

= nmkΔI+IO, and as a result of flowing to negative riiJRs, the output voltage is V
out=Vcc −Rs (n m kΔI + 10
)=−nmk(R,Δ■)+(νCCR51o). As can be seen from the above equation, only the AC component of the human input signal of the output voltage Vout is connected to the control voltage input terminal IA.

The gain is controlled by nmk times by independently controlling the control voltages applied to IB and 2A, 2B and 3A, and 3B, but the DC voltage of the input signal is constant.

The current consumption in the above conventional example is the current consumption of the voltage-current conversion circuit of 10 and the current of the first, second, and third constant current sources of 3XI.
. It was 4xlo which was added.

[Problem that the invention seeks to solve]

In recent years, in integrated circuits, the degree of integration has been increasing and the current consumption has increased, resulting in thermal constraints, and there is also a growing demand for reducing the current consumption in integrated circuits as much as possible from the viewpoint of energy conservation. In the conventional gain control circuit that can perform gain control using three types of gain control voltages, the current ■corresponds to the DC component of the human input signal. There was a problem in that the current consumption was four times that of the previous one.

The present invention was created in view of the above problems, and
It is an object of the present invention to provide a gain control circuit that performs gain control using three types of external control voltages, which reduces this current consumption and has the same effect as the conventional example.

[Means for solving problems]

Means for achieving the above object in the present invention includes a voltage-current conversion circuit that converts an input signal into a current, and a first and a second voltage-current conversion circuit.
a first differential pair consisting of a transistor, a second differential pair consisting of a third and a fourth transistor, and a third differential pair consisting of a fifth and sixth transistor. and the seventh
and an eighth transistor, a fifth differential pair consisting of a ninth and a first O transistor, and a sixth differential pair consisting of an eleventh and twelfth transistor. It is equipped with a differential pair and a constant current source, the voltage-current conversion circuit output and the common emitter of the first differential pair are connected, and the constant current source and the second
The common emitters of the differential pair of are connected, the connection point between the base of the second transistor and the base of the third transistor is one of the first control voltage input terminals, and the base of the first transistor and the base of the fourth transistor are connected. The connection point with the base of the transistor is the other one of the first control voltage input terminals, the collector of the first transistor and the common emitter of the third differential pair are connected, and the collector of the fourth transistor and the common emitter of the third differential pair are connected. Connect the common emitters of the differential pair and connect the base of the sixth transistor and the seventh transistor.
The connection point with the base of the fifth transistor is one of the second control voltage input terminals, and the connection point between the base of the fifth transistor and the eighth transistor is one of the second control voltage input terminals.
The connection point with the base of the transistor is the other one of the second control voltage input terminals, the collector of the fifth transistor is connected with the common emitter of the fifth differential pair, and the collector of the eighth transistor is connected with the common emitter of the fifth differential pair. The common emitters of the differential pair are connected, the connection point between the base of the tenth transistor and the base of the eleventh transistor is one of the third control pressure input terminals, and the connection point between the bases of the ninth and twelfth transistors is set as one of the third control pressure input terminals. The connection point is the other of the third control voltage input terminal, and the collector of the ninth transistor, the collector of the eleventh transistor, the collector of the third transistor, and the collector of the seventh transistor are connected. This is a gain control circuit characterized by having a gain control output terminal.

[Effect]

In the above configuration, the first control voltage input terminals IA, IB
The first gain control is performed by the control voltage applied to the first and second differential pairs from A second gain control is performed, and a third gain control is performed by a control voltage applied from the third control voltage input terminals 3A, 3B to the fifth and sixth differential pairs.

In the present invention, the common emitter of the sixth differential pair is coupled to the fourth differential pair, and the common emitter of the fourth differential pair is coupled to the second differential pair.
By coupling to the differential pair, the two constant current sources for making the DC potential constant, which were conventionally required in the cylinder 6 and the fourth differential pair, are not required, thereby reducing current consumption.

〔Example〕

An embodiment of the present invention will be described in detail below based on the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, members having the same functions as those of the conventional example will be described with the same reference numerals. First, the configuration will be described. The gain control circuit of this embodiment is a first differential circuit that is composed of a voltage-current conversion circuit that converts an input signal VIN into a current, a first transistor Q, and a second transistor Q2. a second differential pair consisting of a third transistor Q3 and a fourth transistor Q4; a third differential pair consisting of a fifth transistor QS and a sixth transistor Q6; and a seventh differential pair consisting of a fifth transistor QS and a sixth transistor Q6. a fourth differential pair consisting of the transistor Q of A sixth differential pair including a transistor Q r + and a twelfth transistor QIK, and a constant current source are provided. Each transistor constituting the above circuit is exemplified as an npn type.

The voltage-current conversion circuit consists of transistor Q r 3 and resistor R 1
The input signal VIN is connected to the base of the transistor Q + 3, one end of the resistor R1 is connected to its emitter, and the other end is connected to the circuit power supply OV.

The constant current source is composed of transistors Q14 and R2, and a voltage source V is connected to the base of transistor QI4. ', one end of a resistor R8 is connected to the emitter, and the other end of the resistor R2 is connected to the circuit power supply 0. The common emitters of the transistors Q, , Q of the first differential pair are connected to the output of the voltage-current conversion circuit, that is, the collector of the transistor Q13, and the transistor of the second differential pair is connected to the collector of the constant current source transistor Q14. Q.

The common emitter of transistor Q4 is connected, the connection point between the base of transistor Q2 and the base of transistor Q is one of the first control voltage input terminals, and the connection point between the base of transistor Q and the base of transistor Q4 is The other one of the first control voltage input terminals is IB. Also, transistor Q
, a third differential pair of transistors Qs,
The common emitter of Qb is connected to the collector of transistor Q4, and the transistor Q? of the fourth differential pair is connected to the collector of transistor Q4. , Qa are connected, the connection point between the base of transistor Q and the base of transistor Q7 is one of the second control voltage input terminals, and the base of transistor Q and the base of transistor Q@ are connected. The point is the other one of the second control voltage input terminals 2B.

Further, a fifth differential pair of transistors Q, ,Q, is connected to the collector of the transistor Qs. Connect the common emitter of
A sixth differential pair of transistors Q r r + Q l ! is connected to the collector of the transistor Q. connect the common emitter of transistor Ql and the base of transistor Q
The connection point between the base of the transistor Q1 and the base of the transistor Q1 is assumed to be one of the third control voltage input terminals 3A, and the connection point between the base of the transistor Q and the penis of the transistor Q1□ is the other one of the third control voltage input terminals 3B.

In addition, the collector of transistor Q9 and the transistor Q,
The collector of the transistor Q7, the collector of the transistor Q, and the collector of the transistor Q are connected to each other, and this connection point is connected to the circuit power supply (reference power supply) Vcc via the load R1 and is used as the gain side j111 output terminal. The collector of transistor Q2 and the collector of transistor Q. The collector of transistor QI2 and the collector of transistor QI2 are each electrically connected to reference voltage #Vcc.

The operation of the embodiment with the above configuration will be described. In this embodiment, the first control voltage input terminal IA is connected to the input signal VIN.
, the first gain control is performed by the control voltage applied to the first and second differential pairs from IB, and the control is applied to the third and fourth differential pairs from the second control voltage input terminals 2A and 2B. The second gain control is performed by the voltage, and the third gain control is performed using the voltage.
Third gain control is performed by control voltages applied to the fifth and sixth differential pairs from the control voltage terminals 3A and 3B.

The first gain control, second gain control, and third gain control are controlled independently from each other as described below.

The input signal VIN is input to the bases of the transistors Q and 3 and converted into a current as in the conventional example. Here, V, , -V as in the conventional example. If +Δ■, the collector current of the transistor is ■. −■, +ΔV. Further, in the constant current source constituted by the transistor QI4 and the resistor Rz, the resistor R is set so that a current I0 equal to the DC component of the input signal current flows.

and the constant voltage source V0' is set. Input signal current (t.

10Δ■) is input to the emitter of the first differential pair, and the current I0 of the constant current source formed by the transistor QI4 and the resistor R2 is input to the emitter of the second differential pair.

Now, by using arbitrary control voltages from the first control voltage input terminals IA and IB, the current distribution ratio of the transistors Q1 and C2 is set to:l-. (At the same time, the current distribution ratio of transistors Q4 and C3 also becomes: l-). The transistors Q+ and Qz at this time.

Collector current of C3 and C4 I C1+ I CI
IC3+IC4 are as follows.

■. +=k (Io +ΔI) IC2-(1k) (Io +Δ■) 1c3=(1k)i.

ICJ=kl.

In addition, the current distribution between transistors Q and Q& can be controlled by using arbitrary control voltages from the control voltage input terminals 2A and 2B.
-m (at the same time, the current distribution ratio of transistors Qm and Q is also m:(1-m)), then transistor Qs,
Collector current of Qb, C7, Qe I C5+ T
C6+I C1=I CB are as follows.

IC5=m Ic+=mk (16+Δ1)Ica=
(l m)Ic+ = (1m)k (Io +Δ■) IC? =(1-m)IC4=(1-m)k I.

Ice=m IC4=mk I.

Also, transistors Q, and Q, are controlled by arbitrary control voltages from input terminals 3A and 3B. The current distribution ratio of n:l-n
(at the same time, the current distribution ratio of transistors Ql and QI+ becomes n:l-n), transistor Q9. Ql. ,Q
l1. Collector current of Q+□ IC911CIO+ I
c+ + Icrt are as follows.

1cq-n Ics=nmk No +ΔI)rc+o
-(I n) Ics=(1-n)mk (I
o +Δ1) +c++ = (l n) Ice-(l n)
mkl.

Icrt = n I (11 = nmk I.

Therefore, the current IL flowing through the load Rs is IC'l, ICI, and IC? + Since it is the composite current of IC11, IL =
Ic3+ IC? ”109+IClC11=n
(Io +ΔI) + (1-k)I.

+ (1m) kt.

+ (1-n) mk I.

=nmkΔI+10, and the output voltage Vout is Shout=Vcc-R, (1,+nmkΔI)=-n
mk (RsΔI) + (Vcc Rs Io). This Vou C0 formula is exactly the same as shown in the conventional example, and this circuit is the control voltage input terminal IA.

By three types of control voltages applied from IB and 2A, 2B and 3A, and 3B, only the AC signal component Δ■ of the input signal VI is independently gain controlled, and the DC component v of the input signal v0 is
It can be seen that 0 is always constant.

The above is an example of the present invention, and the present invention is not limited to the above-mentioned example.
It goes without saying that even if, for example, a pnp transistor is used as the transistor constituting the above circuit, exactly the same effect will be produced.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, gain control can be performed independently on the input signal using three types of control voltages as in the conventional example, and the current consumption is reduced by the DC component of the input signal compared to the conventional example. The current that used to be four times the DC current corresponding to the
It has the effect of Particularly when the present invention is used in an integrated circuit or the like, it exhibits many effects such as facilitating thermal design and increasing the degree of integration by saving current consumption.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a gain control circuit diagram of a conventional example. Q,...first transistor QX-...second transistor Q,...third transistor Q,...fourth transistor Q,...fifth transistor Q,...th 6th transistor Q, . . . seventh transistor Q, . . . eighth transistor Q, . . . ninth transistor Ql. . . . 10th transistor Glt+ . . . 11th transistor QI! ...12th transistor Q, s...transistor (voltage-current conversion circuit) Q,...
...Transistor (constant current source) R1...Resistor (voltage-current conversion circuit) R,...Resistor (constant current source) vo...Human power signal Vout...Output voltage Vo'...Voltage source ( constant current source) IA, IB...first control pressure input terminal 2A, 2B...
・Second control pressure input terminals 3A, 3B...Third control pressure input terminals Fig. 1

Claims (1)

[Claims] a first differential pair consisting of a voltage-current conversion circuit that converts an input signal into a current, a first and a second transistor, and a third
a second differential pair consisting of a and a fourth transistor; a third differential pair consisting of a fifth and a sixth transistor;
A fourth differential pair includes a seventh and eighth transistor, a fifth differential pair includes a ninth and tenth transistor, and a fifth differential pair includes an eleventh and twelfth transistor. 6
a differential pair and a constant current source, the voltage-current conversion circuit output and the common emitter of the first differential pair are connected, the constant current source and the common emitter of the second differential pair are connected, The connection point between the base of the second transistor and the base of the third transistor is one of the first control voltage input terminals, and the connection point between the base of the first transistor and the base of the fourth transistor is the first control voltage input terminal. , the collector of the first transistor is connected to the common emitter of the third differential pair, the collector of the fourth transistor is connected to the common emitter of the fourth differential pair, and the collector of the fourth transistor is connected to the common emitter of the fourth differential pair. The connection point between the base of the sixth transistor and the base of the seventh transistor is one of the second control voltage input terminals, and the connection point between the base of the fifth transistor and the base of the eighth transistor is the second control voltage input terminal. The other control voltage input terminal is connected to the collector of the fifth transistor and the common emitter of the fifth differential pair, the collector of the eighth transistor is connected to the common emitter of the sixth differential pair, and the collector of the fifth transistor is connected to the common emitter of the sixth differential pair. The connection point between the base of the transistor and the base of the eleventh transistor is one of the third control voltage input terminals, and the connection point between the bases of the ninth and twelfth transistors is one of the third control voltage input terminals. On the other hand, a gain characterized in that the collector of the ninth transistor, the collector of the eleventh transistor, the collector of the third transistor, and the collector of the seventh transistor are connected, and this connection point is used as a gain control output terminal. control circuit.