JPS6174406A - Differential amplifier circuit - Google Patents

Abstract

PURPOSE:To attain ease of setting of a bias to the next stage and to obtain a large amplification factor by constituting a differential output type differential amplifier circuit through the combination of two active load circuits comprising current mirror circuits n opposite direction substantially. CONSTITUTION:When a positive input signal is fed to a transistor (TR) 11, a collector voltage Vc1 of the TR11 is dropped, a collector voltage Vc2 of a TR12, resulting that the forward voltage drop VF1 of a TR16 is increased and a forward voltage drop VF2 of a TR18 is reduced. Then since a collector-emitter voltage VCE of a TR17 whose base is common to that of the TR16 is decreased, the voltage VF2 of the TR18 is decreased further and a collector-emitter voltage VCE of the TR19 is increased conversely, then the voltage Vc1 of the TR11 is decreased further. The gain is increased by forming a current mirror circuit while adding the TRs17, 19 to the TRs 16, 18. Then the bias current of the next stage is set by the TR16, 18 of diode connection connected to the collector of the TR11, 12 so as to obtain stable operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential amplifier circuit suitable for use, for example, in the case of fabricating a monolithic IC.

[Conventional technology]

Various types of differential amplifier circuits have been proposed in the past, and the ones shown in FIGS. 9 to 11 are examples thereof. That is, in FIG. 9, transistors (1) and (21) constituting a differential amplifier are provided, the bases of these transistors are connected to the input terminals +31 and (4)K, their emitters are commonly connected, and a constant current source is connected. (5) is connected to the negative power supply terminal -VIJ through the transistor (1).

The collectors of (2) are respectively connected to the positive power supply terminal +61 through the transistor +61 having a diode-connected configuration, and the f-power.
Connect to VCC. and transistors (1) and (2
Output terminals (81 and (91) are taken out from the collector side of ), respectively.

In the IEIO diagram, the collectors of transistors (11 and (21) constituting the differential amplifier are connected to resistors α, respectively.
Connect the positive power supply terminal +VCCK through α and αυ, and output terminal (8) from the collector side of transistors (1) and +21.

K to take out (9).

However, in the case of Fig. 9, although it is suitable for direct connection with the next stage, it has the disadvantage of not being able to obtain a large gain.
In the case of FIG. 0, the gain can be sufficiently obtained, but it is difficult to connect directly to the next stage due to the resistive load, and there is a drawback that the output stage of the push-pull configuration cannot be easily connected directly. Therefore, a device as shown in FIG. 11 can be considered as having both of these advantages. That is, in FIG. 11, transistors (1), transistors (6) with diode connection configuration provided on the collector sides of +21,
The bases of (7) are interconnected, and the common connection point is connected to the transistor (6) via the resistor (101 and αD).
, (connected to each collector side of 71).

In this way, this circuit can provide a large gain and can be easily connected directly to the next stage. However, in the case of this circuit, in order to obtain a large gain, the resistor aα is required.

(Ill requires a resistance value of several hundred ohms or more, and therefore, when fabricated into a monolithic IC, a highly accurate high resistance requires a large area, resulting in an inconvenience that it becomes expensive when fabricated into an IC.

Also, as can be said of the circuits shown in FIGS. 9 to 11 above, in order to increase the gain, it is sufficient to increase the current of the constant current source (5); Since the pace current of the transistors (1) and +21 increases, this is disadvantageous when constructing a multi-stage directly connected circuit, and there is also the disadvantage that current consumption as a collector current increases.

[Problem that the invention seeks to solve]

The present invention has been made in view of these points, and provides a differential amplifier circuit that has a simple structure, can be integrated into an IC, and is suitable for extremely low voltage driving.

[Means for solving problems]

This invention relates to first and second transistors αυ, α2 constituting a differential amplifier, and these transistors αυ, az
A transistor αe and a third transistor αD as a first diode, a transistor a& as a second diode, and a fourth transistor σ are connected to the main electrode or collector side of the transistor and constitute a current mirror circuit.
9, the first and fourth transistors an, a
The first output is taken out from the main electrode or collector side of the transistor ti, and the second output is taken out from the main electrode or collector side of the second and third transistors a'a and an.

[Effect]

A differential input signal is supplied to the transistors αB and a2 that constitute the differential amplifier, and from the collector side of the transistor αυ, the transistors α11 and (19) have a large gain that substantially depends on the amplification factor and the operating resistance of the transistor ae. The first output is taken out, and a second output with a large gain that substantially depends on the amplification factor of the transnostar uz, (17) and the operating resistance of the transistor αε is taken out from the collector side of one transistor α2. The bias current of the next stage to which the first output is supplied is substantially determined by the forward drop voltage of the diode-connected transistor stop provided on the collector side of the transistor αυ, while the bias current of the next stage to which the second output is supplied is The bias current of the stage is substantially determined by the voltage drop in the head direction of the diode-connected transistor αg provided on the collector side of the transistor α2.This sets the bias for the next stage, which is a characteristic of a diode load. A push-pull differential amplifier circuit is constructed, which has both the ease of operation and the ability to obtain a large amplification degree, which is a characteristic of active loads.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on FIGS. 1 to 8.

FIG. 1 shows the basic circuit of the present invention, and in the same figure, first and second transistors α1) and f1? that constitute a differential amplifier are connected to each other. J and these transistors (
Each pace of Ill, a'a is input to the input terminal (13, (1
41, and connect each emitter in common to create a constant current source α9.
Connect to the negative power supply terminal -VEE via. Further, the collector side of the transistor αυ is connected to the positive power supply terminal VCC via the collector emitter of the transistor αe serving as a first diode. The pace-collector of transistor ae is then interconnected. In other words, Ridran Zosta αe is used as a diode. Further, a third transistor αη is provided corresponding to this transistor 161, and the respective paces of both transistors are interconnected. Connect the emitter of the transistor (In to the positive power supply terminal + VCCti
c connection, and its collector is connected to the collector side of transistor a2. ), transistor α61, an
This constitutes a current mirror circuit.

In addition, the collector side of the transistor (1z is connected to the positive power supply terminal +VCC K via the collector emitter of the transistor a8 as a second diode, and the pace and collector of this transistor αa are interconnected), and the transistor U is a diode. It is used as a closure. Also, a fourth transistor (19
and interconnect each pace of both transistors. Connect the emitter of transistor σ9 to the positive power supply terminal +vcc K
and its collector is connected to the collector side of the transistor αυ. The knob, transistors a&, and σ9 constitute a current mirror circuit different from the one described above. Then, the output terminal Q1J is taken out from the common connection point between the collectors of the transistors aυ and (C9), and the output terminal Q1J is taken out from the common connection point between the collectors of the transistors α2 and αη.

Now, the collector voltage of the transistors συ and σ2 when there is no signal is VCl + "C2, and the collector current of each transistor is IC1l.
11. The current flowing into the emitter side of IC2 and transistor αG-α9. ■z, ■3. Step 4. If the current flowing through constant current source α9 is II, then ICI = IC2・ICI
+ IC2= IE and Nasi, further Ic1= IllI4
* Icz = I2+ C3 theal.

Since the transistors (161 and η, αυ and αj each constitute a current mirror circuit, It ” I
The relationship is 2*l3=I4. In such a state, the forward drop voltage VF1 of the transformer CI nostar (Le) is determined by , and the forward drop voltage VF2 of the C2 transistor αε is determined by −2−.

Next, when a positive input signal from one of the transistors constituting the differential amplifier, for example transistor (IIIK), is supplied, transistor αD turns on and transistor az turns off. As a result, the collector voltage Vc1 of transistor αJ decreases. However, the collector voltage VC2 of the transistor (1z) increases. As a result, the forward voltage drop VFI of the transistor αθ increases, and the forward voltage drop VF2 of the transistor α& decreases.

Then, since the collector-emitter voltage VCE of the transistor (161) and the pace are interconnected decreases, the forward drop voltage vF2 of the transistor (18) becomes even smaller. are interconnected transistors (1!J
On the contrary, the collector-emitter voltage VCE increases, so the collector voltage of the transistor αB is further reduced. In this way, the transistor αη than when the transistor (161, (18+) diode load.

tl! By adding J to create a current mirror circuit configuration, the transistors σu, (
It is possible to increase the change in the collector potential of 1z.

In other words, a large gain can be obtained. As a result, a differential amplifier circuit having a differential output with a large gain is constructed.

The circuit of FIG. 1 consists of a differential amplifier consisting of transistors (111 and α2) shown in FIG. 2A, a current mirror circuit consisting of transistors (18 and S), and a transistor shown in FIG. 2B. α1) , (A circuit consisting of a differential amplifier consisting of 13 elements and a current mirror circuit consisting of one transistor αB is combined by making sure that the diode connection sides that make up the current mirror circuit do not overlap. They are equivalent.

As a result, the increase in the number of elements remains at 2 compared to before the combination)
Despite this, it is possible to achieve greater gain and stability with the same emitter current than any of the conventionally known differential amplifier types with differential outputs, that is, the differential amplifier circuits shown in Figures 9 to 11. Obtainable. That is, in the case of FIG. 1, the gain is that of transistor aD during one half cycle of the input signal.

Due to the amplification factor of α9 and the operating resistance of transistor ae, and in the other half cycle of the input signal, transistor α2.
It is determined by the amplification factor of αD and the operating resistance of transistor a&. In addition, diode-connected transistors (
Since the bias current of the next stage is set by Lθ and 0g, stable operation can be obtained.

Incidentally, as shown in FIG. 2A or B, the transistor 011
If the output is taken out to the next stage from the point where the collectors of σ9 or 0z and αη are connected, the current on the collector side will change, so it is impossible to set the bias current of the next stage. In the case of the figure, the diode-connected transistor ti61. The forward drop voltage of σa determines the pace-emitter voltage of the next stage transistor,
Since the bias current is thereby set, the bias for the next stage can be determined. In other words, it is possible to substantially adjust the bias of the next output stage.

In this case, the current as the constant current source 151 is about 200 μA in a normal amplifier, but in this case, the current is about 20 μA.
It is considered to be quite small. Incidentally, when a large current flows through the circuit shown in Figure 1, the apparent resistance value of the diode-connected transistors 116+ and u decreases, making it impossible to obtain any gain (this makes high voltage drive impossible. This circuit is suitable for low-pressure driving.

FIG. 3 shows another embodiment of the present invention, in which a diode-connected transistor (161) is used.

Resistors connected in series on each emitter side of aS, I21
A resistor 1 and a resistor (c) are provided, and the connection point of these resistors is connected to the other transistor σ constituting the current mirror circuit.
This is the case where it is connected to the emitter side of α9.

In this case, resistors ■, ■ and CD, 123) have the same value, and the relationship of resistor ■, <21) is 0. I X R2≧R1)O. In this circuit, the gain is essentially the resistor ■, I21)K
By inserting these resistors, the forward voltage drop of the transistors ae and aS as diodes increases from the forward voltage drop of α9 of the transistor a, which is an active element, and the voltage of the transistor aη, (1g Since the current on the collector side can be increased, the gain can be increased accordingly.

FIG. 4 shows another embodiment of the present invention. In this embodiment, the transistor (161, αη, l)" (18
1゜09 commonly connected emitters and positive power supply terminal +
This is a case where resistors 24) and (e) are inserted between the VCC and VCC. Incidentally, at this time, equivalent resistors (2) and (to) are used. And when you want a different current to flow, resistor 124), 'Ill! ! The value of 19 may be changed.

FIG. 5 shows another embodiment of the present invention, in which resistors (I) are connected between the emitters of the transistors α, αη, a&, αj and the positive power terminal )
, @, @, and e23 are inserted. In this case, resistor (c) and 弼 are equal, and resistor (5).

The resistance values of (2) are also equal, and the resistance values of resistors (a) and (5) are equal to 7, or the resistance value of resistor (a) is set to R3.
, if the resistance value of the resistor is R4, then 0.9 x R3
≧R4. In this case, if the values of resistors (a) and (5) and the values of the resistors (a) and (b) are considered, the gain can be increased for the same reason as in FIG. 3, and the gain can be easily adjusted.

FIG. 6 shows another embodiment of the invention, in which a resistor (7) is provided on the emitter side of the transistors αθ and αS.

(Inserting 311 and adding another constant current source cz, C(
3) is inserted on the collector side of the transistor (111, α2), that is, on the collector side of the diode 0-connected transistor (161, α&).

The reason for inserting these constant current sources OZ and a is as follows. That is, these constant current sources Oa
, considering the case where there is no can, the current flowing through the transistors αυ and a'a that constitute the differential amplifier, that is, the diode-connected transistor I connected to its collector side.
The bias current of the next stage is determined by the current flowing through ie and α&. Therefore, the output of the next stage is necessarily this diode-connected transistor αe.

is substantially determined by the current flowing through aS. Therefore, in order to increase the output of the next stage, another constant current source ez,
ca is provided, and the current is pumped in to increase the current flowing through the diode-connected transistors (1e, α♂, which causes the diode-connected transistors (L
By increasing the voltage drop at fij and f13, the bias current of the next stage is increased and the output is increased. Therefore, for this circuit,
High gain can be obtained and any bias voltage can be used. In addition, in this case, the resistor (to), I3
The value of 1+ is equal to (7), and the constant current source Q2,
The same current is used for C33+.

FIG. 7 shows yet another embodiment of the invention, in which diode-connected transistors n61. a
This is the case where resistors G4J and i are inserted on the pace side of Fj, respectively. By inserting these resistors (2) and (2), the pace voltage increases, and the voltage obtained at the output terminals eυ and (2) can be increased. In this case, resistors of equal value are used.

FIG. 8 shows an example of a specific circuit for measuring the gain, in which a resistor (to) and a DC power supply Gη are connected between the input terminal a3 and the ground. The resistance value of this resistor (G) is 10Ω
, the voltage of the DC power supply (371 is 1.5V), and the capacitor (to) connected in series in parallel with these and the signal source C3.
Connect 1. The frequency of the signal source in this case is, for example, 315 Hz. In addition, a current of 20 μA is passed through the constant current source (151). Furthermore, a 1000 μF capacitor 4G is connected between the input terminal α and the ground, and a Ω resistor (411 and a voltmeter □□ Connect □.

In addition, connect the transistors i43 and (441) constituting the next stage to the output terminals ■ and (2υ), and connect the emitters of the transistors (c) and (4) to the positive power supply terminal + VCC. Connect each collector to the ground side through the collector emitter of the transistor (4E9, (46J).The transistor (46) has a diode connection configuration.Then, insert each circuit into the part surrounded by the broken line. Then, measure the
FIG. 8 shows a case where the circuit of FIG. 1 is inserted.

The measurement results are shown in Tables 1 and 2 below.

Table 1 Table 2 As can be seen from Table 1 above, in the case of the conventional circuit shown in Figure 9, there is only a gain of 25.5 dB, so the first
If a resistive load is used as shown in Figure 0, a gain of 51.5 dB can be obtained, but in this case, the current flowing through the output stage (next stage) K is unstable and is not practical.

In addition, in the case of Fig. 11 which solves these drawbacks, the resistor aCfi, (11) (7) value is 100KQ toj
Root 5.3.3dB, 59.4d when set to 510Ω
Although a large gain can be obtained with resistor t101. Since it is necessary to increase the value of αB, it is not practical, and especially when monolithic IC is considered, it requires a large area and is expensive, so it is not practical.

On the other hand, as can be seen from Table 2, K, the first
In the case shown in the figure, a gain of 53.5 dB is obtained despite the simple circuit configuration. Also, as shown in FIGS. 2 and 4, a diode-connected transistor αG.

fi8) and transistors αn, which form a pair with these, respectively.
It can be seen that by creating a ratio between σ9 and σ9 using a resistor, the gain is increased by about 10 dB compared to the basic circuit shown in FIG.

Moreover, compared to the case of 100 sets in FIG. 11, the gain in the case of FIG. 3 was increased by about 10 dB or more even though the area occupied on the IC chip was smaller.

〔Effect of the invention〕

As described above, according to the present invention, one differential output type differential amplifier circuit is constructed by substantially combining two active load circuits using current mirror circuits, which conventionally had single outputs, in opposite directions. It becomes easy to set the bias for the next stage, which is a feature of a diode load, and it also becomes possible to have a large amplification factor, which is a feature of an active load.

Further, as in the embodiment shown in FIG. 6, by separately providing a constant current source and changing its current, it becomes possible to freely adjust the bias current of the output stage disposed at the next stage. The bias of the output stage can be adjusted using this constant current source.
The invention is similarly applicable to other circuits.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a connection diagram showing one embodiment of the present invention, Fig. 2 is a connection diagram for explaining the invention, and Figs. FIG. 8 is a circuit configuration diagram for measuring gain, and FIGS. 9 to 11 are connection diagrams each showing an example of a conventional circuit. αB, α2 are transistors forming a differential amplifier, +t
e, αη and α8), (I9 is a transistor that constitutes a current mirror circuit, α9 is a constant current source. Go to Figure 1, Figure 3, Figure 4, and Figure 11)
To 1tFigure 5Figure 6Figure 7Figure 8Figure 9Figure 10

Claims (1)

[Claims] 1. First and second transistors forming a differential amplifier, a first diode, a third transistor, and a second transistor connected to the main electrodes of the transistors and forming a current mirror circuit, respectively. a diode and a fourth transistor, and a first
What is claimed is: 1. A differential amplifier circuit, wherein the output of the differential amplifier circuit is taken out from the main electrodes of the second and third transistors, and the second output is taken out from the main electrodes of the second and third transistors. 2. Claims in which the current mirror circuit has first and second resistors connected to the first diode and the main electrodes of the third transistor, and the second diode and the main electrodes of the fourth transistor, respectively. The differential amplifier circuit according to item 1. 3. The differential amplifier circuit according to claim 1, wherein the current mirror circuit has third and fourth resistors connected to the main electrode of the first diode and the main electrode of the second diode, respectively. 4. The current mirror circuit has a fifth diode connected in series to the main electrode of the first diode and the main electrode of the second diode, respectively.
and a sixth resistor, and a seventh and eighth resistor, the connection point of the fifth and sixth resistors is connected to the main electrode of the third transistor, and the connection point of the seventh and eighth resistors is connected to the main electrode of the third transistor. 2. The differential amplifier circuit according to claim 1, wherein the connection point is connected to the main electrode of the fourth transistor.