JPH01183206A - amplifier circuit - Google Patents

Abstract

PURPOSE:To obtain the amplification output of a high driving capacity and a wide dynamic range by connecting a load resistance which divides an excess current from a collector in one of bipolar transistors generating a differential couple to a specified position. CONSTITUTION:The load resistance RL which consists of an input circuit part 1 and an output circuit part 2 and which drives the excess current of a mapping output current Ic2 in a current mirror 11 from the collector of a second bipolar transistor Q2 is connected between the collector of the transistor Q2 and the emitter of a bipolar transistor Q10 generating an emitter follower circuit. Since a change in the current which is current-divided into the load resistance RL from the current mirror 11 can be reduced, the action of the current mirror 11 can be held in normal, and the enlargement of the dynamic range is attained with making the most use of a merit that the amplification output of the high driving capacity can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technology that is effective when applied to amplifier circuits and furthermore, video band amplifiers, such as ICs (semiconductor integrated circuits) for video switches. (Radio Gijutsu Sha rVTR Related Basic Course, published September 16, 1980, pp. 209-210)
.

[Prior art] For example, Radio Gijutsusha rV published on September 16, 1980.
As described in ``TR-Related Basic Course,'' pages 209-210, VTRs (video tape recorders) use IC-based wideband amplifiers in the part that performs video signal switch operations.

Prior to the present invention, the present inventors developed the following amplifier circuit for use in this type of application.

FIG. 3 shows an outline of the amplifier circuit developed by the present inventors.

The amplifier circuit shown in the figure consists of an input circuit section 1 and an output circuit section 2.

The input circuit section 1 includes first and second bipolar transistors Ql, Q2, . current mirror 1
1. It is composed of a load resistor RL, etc. The current mirror 11 is a lateral structure pnp bipolar transistor Q31. Q41, the collector current Icl of the first bipolar transistor Q1 is controlled by a predetermined ratio (
1: A current Ic2 mapped by 1) is supplied to the collector of the second bipolar transistor Q2. Load resistance R
L shunts surplus current that cannot flow into the collector of the mapping output current Ic2 supplied to the collector of the second bipolar transistor Q2.

The output circuit section 2 is composed of an emitter follower circuit using a bipolar transistor Q10, etc.
The output voltage Vc2 appearing at the collector of the bipolar transistor Q2 is impedance-converted and output.

In addition, in the figure, Vin indicates the input voltage of the amplifier circuit, and Vout indicates the output voltage of the amplifier circuit.

Further, Vcc indicates a power supply potential, VREF indicates a reference bias potential, and GND indicates a reference potential.

In the amplifier circuit described above, the collector supply current Ic2 of the second bipolar transistor Q2 is connected to the current mirror 11.
, the second bipolar transistor Q1 is increased according to the collector current Icl of the first bipolar transistor Q1.
A relatively large drive current Is can be taken out from the collector of the bipolar transistor Q2 and inputted to the output circuit section 2 of the next stage. This results in
A sufficient drive current is applied to the output circuit section 2 to obtain an amplified output with high drive capability.

Note that the above-mentioned technique is a technique studied by the present inventors and is not a known technique.

[Problems to be Solved by the Invention] However, the inventors have found that the above-mentioned technique has the following problems.

That is, in the circuit shown in FIG. 3, a load resistor RL that shunts surplus current from the collector of the second bipolar transistor Q2 is connected between the collector of the second bipolar transistor Q2 and the reference bias potential VREF. . Therefore, when the output voltage Vc2 appearing at the collector of the second bipolar transistor Q2 increases, the magnitude of the current IR shunted to the load resistor RL exceeds the magnitude of the mapping output current Ic2 of the current mirror 11, and the current mirror 11 will not be able to operate properly.

Therefore, in the circuit shown in FIG. 3, it is not possible to increase the amplitude range, that is, the dynamic range, of the output voltage V c 2 taken out from the collector of the second bipolar transistor Q2, and this reduces the dynamic range of the amplifier circuit. This has become an impediment to its expansion.

An object of the present invention is to provide an amplifier circuit of circuit type in which the collector supply current of bipolar transistors forming a differential pair is given by a current mirror, and the dynamic range is The goal is to provide technology that enables the expansion of

The above and other objects and novel features of the present invention will become clear from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows.

That is, the collector current of the first bipolar transistor is mapped and supplied to the second bipolar transistor forming a differential pair with the first bipolar transistor, and the surplus current is shunted from the collector of the second bipolar transistor. A load resistor is connected between the collector of the second bipolar transistor and the emitter of the bipolar transistor forming the emitter follower of the next stage. That is what it is.

[Function] According to the above-described means, it is possible to reduce the change in the current shunted from the current mirror to the load resistor, so that even if the output voltage appearing at the collector of the second bipolar transistor has a large amplitude, the current mirror remains unchanged. will be able to maintain normal operation.

This makes it possible to expand the dynamic range of an amplifier circuit that uses a current mirror to supply the collector current of bipolar transistors forming a differential pair, while taking advantage of the ability to obtain an amplified output with high drive capability. One purpose is achieved.

[Examples] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

In each figure, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows an amplifier circuit according to one embodiment of the present invention.

First, the basic configuration will be explained. The amplifier circuit shown in the same figure consists of an input circuit section 1 and an output circuit section 2, similar to the one shown in FIG.

The input circuit section 1 includes first and second bipolar transistors Ql and Q2, which form a differential pair, and a current mirror 1.
1. It is composed of a load resistor RL, etc. The current mirror 11 is a pnp bipolar transistor Q3. A current Ic2 formed by the collector current Ic1 of the first bipolar transistor Q1 is mapped at a predetermined ratio (1:1) to the second bipolar transistor Q2.
supply to the collector. The load resistor RL shunts surplus current that cannot flow into the collector of the mapping output current Ic2 supplied to the collector of the second bipolar transistor Q2.

The output circuit section 2 is composed of an emitter follower circuit using a bipolar transistor QIO, etc.
The output voltage Vc2 appearing at the collector of the bipolar transistor Q2 is impedance-converted and output.

In addition, in the figure, Vin indicates the input voltage of the amplifier circuit, and V out indicates the output voltage of the amplifier circuit.

Further, Vcc indicates a power supply potential, and GND indicates a reference potential.

With the configuration described above, the second bipolar transistor Q1 increases in accordance with the collector current Icl of the first bipolar transistor Q1.
Collector supply current Ic of bipolar transistor Q2
By inputting a portion of 2 to the output circuit section 2 in the next stage as the drive current generator 8, it is possible to provide a sufficient drive current to the output circuit section 2 and obtain an amplified output with high drive capability. ing.

Here, in the amplifier circuit of the embodiment shown in FIG.

A load resistor RL for shunting the mapping output current Ic2 of the current mirror 11 from the collector of the second bipolar transistor Q2 is connected to the collector of the first bipolar transistor Q2.
and the emitter of a bipolar transistor Q10 forming an emitter follower circuit.

As a result, the output voltage Vc appearing at the collector of the second bipolar transistor Q2 is applied across the load resistor RL.
Instead of the difference between 2 and VREF, the base-emitter voltage VBE of the bipolar transistor QIO forming the emitter follower circuit is applied. Therefore, a nearly constant current IR is shunted to the load resistor RL regardless of the magnitude of the output voltage Vc2. As a result, even if the output voltage Vc2 has a large amplitude within the range of the power supply potential Vcc and the reference potential GND, the current mirror 1
1 will be able to maintain normal operation.

As described above, the amplifier circuit of the embodiment shown in FIG. In addition to providing amplified output, it is also possible to obtain a wide dynamic range.

FIG. 2 shows an amplifier circuit according to a further preferred embodiment of the invention.

The amplifier circuit shown in the figure is a wideband amplifier circuit formed as a video switch IC, and includes npn bipolar transistors Ql, Q2. Q5. Q6゜Ql, Q9. QIO
1pnp bipolar transistor Q3. Q4. Q8. Q
ll, resistors RL, R1 to R4, and the like. Here, both the pnp and npn bipolar transistors have a vertical structure.

In the figure, Ql and Q2 constitute a differential pair.

Ql is driven into conduction by the input voltage Vin, and Q2 is
It is driven to conduct in a complementary manner to l.

Q3. Q4 forms a current mirror 11.

This current mirror 11 supplies a current obtained by mapping the collector current of Ql at a predetermined ratio (1:1) to the collector of Q2.

Q5 and R1, Q6 and R2, and Q9 and R4 each form a constant current circuit that flows a current determined by a predetermined control voltage Ve.

Resistor R3 defines the isometric transconductance of the differential pair of Ql and Q2.

QIO and Qll constitute an output stage of npn and pnp complementary push-pull type circuits. In this case, Q10, which is an npn bipolar transistor, forms an emitter follower circuit that converts the impedance of the output voltage Vc2 appearing at the collector of Q2 and outputs it. Qll, which is a pnp bipolar transistor, also forms a kind of emitter follower circuit. This Qll is -Q7. It is driven by Q8 complementary to Q10.

Ql transmits the output voltage Vc2 appearing at the collector of Q2 to the emitter side of Q8 by emitter follower operation. Q8 operates to draw base current from Qll when the voltage transmitted to its emitter decreases. Thereby, Qll is driven complementary to Q10. In other words, QIO and Qll are B
A push-pull type linear output circuit is configured by driving operation.

A load resistor RL is connected between the collector of Q2 and the emitter of Q10, and in this state, the surplus of the mapping output current Ic2 of the current mirror 11 is shunted from the collector of Q2.

Furthermore, in the embodiment, the output voltage Vout taken out from the common emitter connection point of QIO and Qll is fed back to the base of Q2. As a result, the overall profit of the amplifier circuit is set to 1 (Vout/Vin=1),
A video switch is configured that unilaterally transmits a wideband video signal from an input side to an output side while converting impedance.

Furthermore, the amplifier circuit according to the embodiment shown in FIG. By adopting a vertical structure for the transistor, the operating speed is increased and transmission characteristics over a very wide band can be obtained.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. For example, the current mirror 11 and the like can be constructed from MOS transistors.

The above explanation has mainly been about the case where the invention made by the present inventor is applied to an amplifier circuit for a video switch, which is the background field of application, but the invention is not limited thereto.

For example, it can be applied to applications that handle wideband signals other than video signals, such as a preamplifier for a counter.

[Effects of the Invention] The effects obtained by typical inventions disclosed in this invention are briefly explained below.

That is, it is possible to obtain an amplified output with high driving ability and a wide dynamic range. This effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of an amplifier circuit according to an embodiment of the present invention, FIG. 2 is a diagram showing an amplifier circuit according to a more preferred embodiment of the present invention, and FIG. 3 is a diagram showing an outline of an amplifier circuit according to an embodiment of the present invention. FIG. 3 is a diagram showing an amplifier circuit. 1...Input circuit section, 11...Current mirror. 2... Output circuit section, Ql, Q2... NPN bipolar transistor with vertical structure forming a differential pair, QI
O... Vertical structure npn bipolar transistor that forms an emitter follower circuit in the output circuit section, Qll
・・・・P of vertical structure that operates complementary to QIO
np bipolar transistor, RL...load resistance,
VREF...Reference bias potential.

Claims (1)

[Claims] 1. It has an input circuit section and an output circuit section, and the input circuit section has first and second bipolar transistors that form a differential pair with each other, and a collector current of the first bipolar transistor. It has a current mirror that maps and supplies the current to the collector of the second bipolar transistor, and a load resistor that shunts surplus current from the mapped output current of this current mirror, and the output circuit section appears at the collector of the second bipolar transistor. It has an emitter follower circuit that converts the output voltage into impedance and outputs it, and further, the load resistor is connected between the base of the second bipolar transistor and the emitter of the bipolar transistor forming the emitter follower circuit. An amplifier circuit characterized by: 2. The amplifier circuit according to claim 1, wherein the output of the output circuit section is fed back to the base of the second bipolar transistor. 3. The output circuit section consists of an npn bipolar transistor and a p
3. The amplifier circuit according to claim 1, wherein the amplifier circuit is constituted by a complementary push-pull type circuit of np bipolar transistors. 4. The output circuit section consists of an npn bipolar transistor and a p
Claims 1 to 3 are characterized in that the transistor is constituted by a complementary push-pull type circuit of np bipolar transistors, and both transistors are bipolar transistors having a vertical structure. Amplification circuit.