JPS58182907A - Amplifier - Google Patents

Abstract

PURPOSE:To lighten a load and to reduce a loss by inserting a resistance dividing circuit into a negative feedback loop and leading plural different-level amplification outputs out of this resistance dividing circuit. CONSTITUTION:A transistor TR42 and a resistance 44 constitute the output circuit of an amplifier and the amplification output of this output circuit is fed back to the input side of the negative feedback loop 46 negatively. The resistance dividing circuit 54 is inserted into this loop 46, and this circuit 54 is constituted by connecting resistances 56 and 58 in series. The output of this amplifier is led out from the 1st output terminal 60A connected to the collector of the TR42 and the 2nd output terminal 60B formed at the connection point between the resistances 56 and 58. Consequently, two in-phase outputs are obtained without providing an additional circuit such as an attenuator at the outside of the amplifier. Thus, the load on the amplifier is lightened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier, and more particularly to an amplifier that makes it possible to take out a plurality of outputs from within a negative feedback loop.

FIG. 1 shows an amplifier for obtaining two in-phase outputs from one input signal. A signal applied to input terminal 2 (1) is amplified by amplifier 4 and then taken out from output terminal 8A via capacitor 6.

An attenuator 14 consisting of a series circuit of resistors 10 and 12 is installed at the output portion of this amplifier 4, and an output terminal 8B is formed for taking out an output different from the above output.

When output is taken out from this output terminal 8B, a load resistor 16 is connected to this terminal 8B. In addition,
A resistor 18 and a capacitor 20 connected to the input side of the amplifier 40 constitute a feedback circuit.

In this way, when extracting two or more in-phase outputs with one amplifier 4, it is necessary to install an attenuator 14 on the output side of the amplifier 4, but in this case, the internal resistance 22 of the amplifier 4,
Since the combination of the resistor 1O112 of the attenuator 14 and the load resistor 16 is added as a load, there is a drawback that the loss increases.

An object of the present invention is to provide an amplifier that makes it possible to take out a plurality of outputs without externally connecting an attenuator, reduces load, and reduces loss.

(2) This invention inserts a resistor divider circuit into the negative feedback loop that feeds back the amplified output to the input side, and extracts a plurality of amplified outputs with different levels from the resistor divider circuit to the outside, or outputs a plurality of amplified outputs from the next stage such as an amplifier. It is characterized by being directly connected to the circuit to enable input.

Embodiments of the invention will be described in detail with reference to the drawings. FIG. 2 shows an embodiment of the amplifier of the invention. In the figure, the emitters of transistors 24 and 26 are connected in common to a constant current circuit 28, and a drive current is applied to their collectors via a transistor 32 and a diode 34 by a voltage Vcc applied to a power supply terminal 30. ing. An input terminal 36 is formed at the base of the transistor 24, and a constant bias input is applied from a connection point between resistors 38 and 40 connected between the power supply terminal 30 and a reference potential point (GND). There is.

A transistor 42 and a resistor 44 constitute an output circuit of this amplifier, and the amplified output appearing in this output circuit is negatively fed back to the input side in a negative feedback loop 46. A resistor divider circuit 54 is inserted into this negative feedback loop 46 together with a feedback resistor 48 and a capacitor 52 connected to the feedback terminal 50. The resistor divider circuit 54 of this embodiment has two resistors 56 and 58 connected in series. It is configured as follows.

The output of this amplifier is connected to a first output terminal 60A formed at the collector of the transistor 42 and a second output terminal 60A formed at the connection point between the resistors 56 and 58 of the resistor divider circuit 54.
It is designed to be taken out from B respectively.

With the above configuration, two in-phase outputs can be taken out from the negative feedback loop 46 without installing an additional circuit such as an attenuator outside the amplifier. Here, the output appearing at the first output terminal 60A is A V 1 and the output appearing at the second output terminal 60A is A V 1 .
Av2 is the output appearing at the output terminal 60B of the resistor 56.
When the resistance values of the resistor 58 are R1 and R2, and the resistance value of the resistor 48 is Rn, the output has the following relationship.

Av2 = Av 1- R2/ (R+ +R2) However, if the resistance value of the resistor 48 is Rn, the combined value of R1 and R2 (Rt+Rt) in the above (3) is much larger than Rn (Rn<< (Rs +R2 ) ) ,Also,
If the total output of the amplifier is AVO, the output Av1 is A
The condition is that it is much smaller than VO (Avt<<Avo).

In this embodiment, the number of resistors connected to the resistor divider circuit 54 is two, so the output is two. However, by connecting a plurality of resistors of three or more, it is possible to The output can be taken out at any reduction level depending on the resistance ratio of the resistance divider circuit 54.

In addition, the outputs of the first and second output terminals 60A and 60B can be taken out as external outputs of the amplifier, and can also be inputted into a circuit adjacent to the amplifier, such as the next stage amplifier section inside the IC. is also possible. In particular, since the output is taken out from the negative feedback loop 46, there is an advantage that it can also be used as an input bias for the next stage amplifier. Moreover, since an external attenuator is not required, the circuit configuration can be simplified and the load on the amplifier can be reduced (5) (4).

FIG. 3 shows a specific embodiment of the amplifier of the present invention. This embodiment shows an amplifier circuit in which one of the two outputs of the Ni amplifier is a monitor output, and the other is an input to an equalizer amplifier. The same parts as in the previous embodiment are given the same reference numerals. That is, the amplifier 62 corresponds to that of the previous embodiment, the constant current circuit 28 is composed of transistors 64 and 66, and the input terminal 68 is supplied with a driving current. Transistors 24 and 26 are supplied with drive current from transistors 70 and 72, and the resistor 44 is supplied with drive current from transistors 70 and 72.
It consists of The transistor 72 is connected to the transistor 76 in relation to the output current of the transistor 70.
A drive current is provided at 78. The amplified output of the amplifier 62 is taken out as a monitor output to the first output terminal 60A.

The output (second output terminal 60B) appearing at the connection point of the resistors 56 and 58 serves as an input to the equalizer amplifier 80 in the next stage. This equalizer amplifier 80 is a transistor 82
．． 84.86.88.90, (6) 92.94, diode 96 and resistor 98.100.1
02.104, and the feedback terminal 1 of this amplifier 80
An equalizer element consisting of a resistor 10B and a capacitor 110 is connected to 06.

That is, the base of the transistor 82 is connected to the resistor 56.58.
The output of the amplifier 62 is directly connected to the connection point of the equalizer amplifier 80 . Note that the terminal 112 is assumed to be connected to a reference potential point (GND).

With this configuration, the output generated at the connection point of the resistors 56 and 58 of the amplifier 62 is amplified by the equalizer amplifier 80 and given equalizer characteristics, and then output together with the monitor output of the first output terminal 60A. It is taken out from the terminal 114. In this case, the input bias of the equalizer amplifier 80 is connected to the negative feedback loop 46 of the amplifier 62 and shared with the amplifier 62, thereby simplifying the circuit configuration. The circuit of this practical example is constituted by an IC, and the output of the amplifier 62 is inputted to the equalizer amplifier 80 at the next stage without passing through an external attenuator or the like, which is advantageous in terms of the structure.

FIG. 4 shows another embodiment of the amplifier of the present invention.

In FIG. 4, the same parts as in the previous embodiment are given the same reference numerals. In this example, transistor 116.1
Reference numeral 18 constitutes an output circuit for the output A v 2 generated from the resistor divider circuit 54, and is configured to be driven separately from the output circuit for the output A v 1. With this configuration, even if the output AvI reaches a level higher than the applied voltage Vcc and is clipped, as long as the level of the output A V 2 does not reach the level higher than the applied voltage Vcc, the output A
v2 does not clip. That is, if such an output circuit is not installed, the waveform of the output AV2 generated from the resistance divider circuit 54 is usually similar to that of the output Av. However, since an output circuit is installed and driven individually for each output AVI and Av2, each output waveform does not become a similar waveform. Therefore, even if the output Av1 clips and the waveform becomes distorted, Even if there is, the output AV
As long as the level of Av2 does not clip, the waveform of output Av2 can be extracted without distortion (7).

FIG. 5 shows the operating waveforms in this case, where A, B, and C correspond to the respective output generation points and feedback points of the circuit shown in FIG.
Showing point driving. Since the level of the waveform of the output A VI exceeds the applied voltage Vcc, it clips at the broken line portion. On the other hand, the output A V 2 is not clipped like the waveform AV2' shown by the broken line, but is a sine waveform, and a waveform output without distortion is taken out from the output terminal 60B separately from the output from the output terminal 60A. Is possible.

Although the embodiments have been described using an equalizer amplifier or the like as an example, the present invention can be applied to various types of amplifier circuits that require a large number of in-phase outputs.

As explained above, according to the present invention, multiple amplified outputs set to arbitrary reduction levels can be extracted from the negative feedback loop without using an external attenuator or the like.
Moreover, since it uses a negative feedback loop (9) (8), it can also be used as the input bias for the next stage circuit, simplifying its configuration, and eliminating the need for an external attenuator. , the load on the amplifier can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional amplifier, FIG. 2 is a circuit diagram showing an embodiment of the amplifier of the present invention, FIG. 3 is a circuit diagram showing a specific embodiment of the invention, and FIG. FIG. 5 is a circuit diagram showing another embodiment of the amplifier of the invention. FIG. 5 is an explanatory diagram showing operating waveforms of the circuit shown in FIG. 4. 46... Negative feedback loop, 54... Resistance divider circuit. (10) Figure 4 Figure 5 Procedural Amendment 1, Case Indication 1982 Patent Application No. 66540 2, Title of Invention Amplifier 3, ? Relationship with the case of those who commit false claims Patent applicant address: 21 Saiin Mizosaki-cho, Ukyo-ku, Kyoto Name: ROHM Co., Ltd. Representative: Ken Sato Department 4, Agent: 167 Address: 3-2-2 Amanuma, Suginami-ku, Tokyo Ogikubo Kangyo Building 2nd floor 6, subject of amendment 7, content of amendment txt "..." on page 9, line 12 of the specification
Insert the following sentence after ``. [In this example, since the operating point level Vdoc is set higher than the midpoint level between the applied voltage Vcc and the reference potential point (GND) level, only the upper side of the amplitude waveform of the output AVI is clipped. , when the lower amplitude reaches a level lower than the reference potential point level, the waveform portion below the & quasi-potential point level similarly clips. In this case, as in the above operation, the output Av2 is
It can be extracted as a sine waveform without having to be (2) Figure 5 of the drawings is amended as shown in the attached sheet. that's all

Claims (2)

[Claims] (1) A resistor divider circuit is inserted in the negative feedback loop that feeds back the amplified output to the input side, and multiple amplified outputs of different levels are taken out from this resistor divider circuit, or the inputs are directly connected to the next stage circuit. An amplifier characterized by making it possible. (2) A resistor divider circuit is inserted into the negative feedback loop that feeds back the amplified output to the input side, a plurality of amplified outputs with different levels are taken out from this resistor divider circuit, and an output circuit is provided for each of the amplified outputs. An amplifier characterized by being driven individually.