JPH01216607A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To prevent the generation of waveform distortion and to reduce the power consumption by adopting the constitution such that a 1st transistor(TR) whose drain is connected to an input terminal of a current mirror circuit and a 2nd TR whose source is connected to the output terminal of the current mirror circuit. CONSTITUTION:An output current is supplied from a TR Q2 in a positive half cycle of an input signal V1, a drain current of the TR Q2 in this case is the sum of an output current and a drain current of a TR Q4 and a TR Q1 is driven in the OFF state by the input signal V1. Thus, the drain current of the TR Q4 is decreased and the drain current of the TR Q2 is nearly equal to the output current. Moreover, in a negative half cycle of the input signal V1, the output current is supplied from the TR Q4, and as the amplitude of the input signal V1 increases, the drain current of the TR Q1 is increased. Thus, the drain current of the TR Q4 is increased, then the increase in the output current is sufficiently supplied to prevent the generation of wavelength distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier circuit, and particularly to an amplifier circuit suitable for a voltage buffer circuit of an integrated circuit.

[Conventional technology]

Various amplifier circuits of this type have been proposed in the past, and one of them is a circuit known as a source follower circuit as shown in FIG.

This circuit is composed of a transistor Q1 and a constant current source circuit IG2, the source of the transistor Q1 is connected to the ground terminal via the constant current source circuit IG2, and is also connected to the 1 signal output terminal ToK, and the drain is connected to a power supply lightning, The gate is connected to the voltage Vcc terminal, and the gate is connected to the signal input terminal TIK.

The input signal Vl applied to the signal input terminal Tl does not depend on the load resistance and appears as the output signal Vo at the signal output terminal TO with a voltage gain of 1. Therefore, if the load side is set to a low impedance, the power is lower than K. gain can be obtained.

[Problem to be solved by the invention]

In the conventional amplifier circuit described above, the ability to supply a source current to the load side is almost unlimited, but the ability to supply a sink current is regulated by the current value of the constant current source circuit IG2.

Therefore, when the load resistance is low and the amplitude of the output signal Vo is large, waveform distortion occurs, and in order to suppress this waveform distortion, it is necessary to set the current value of the constant current source circuit Io2 large. This inevitably leads to an increase in power consumption, and has the disadvantage that it cannot be applied to integrated circuits with small allowable power consumption.

An object of the present invention is to provide an amplifier circuit that can suppress waveform distortion, reduce power consumption, and expand the range of application.

[Means to solve the problem]

The amplifier circuit of the present invention includes a first transistor of one conductivity type having a gate connected to a signal input terminal and a source connected to a first power supply voltage terminal; a gate connected to the signal input terminal and a drain connected to the first transistor; a second transistor of opposite conductivity type connected to the power supply voltage terminal of the transistor and having its source connected to the signal output terminal;
The third transistor includes third and fourth transistors of opposite conductivity types.
The drain of the transistor is connected as an input terminal to the drain of the first transistor, the drain of the fourth transistor is connected as an output terminal to the signal output terminal, and the sources of the third and fourth transistors are connected as an input terminal to the drain of the first transistor. It has a current mirror circuit connected to a power supply voltage terminal.

Further, a fifth transistor of a reverse conductivity type having a gate connected to the signal input terminal and a drain connected to the first power supply voltage terminal; one end connected to the source of the fifth transistor and the other end connected to the second transistor; A constant current source circuit connected to the power supply voltage terminal of is provided, and the gate of the first transistor is connected to the source of the fifth transistor.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

This embodiment includes a first transistor Q1 of one conductivity type whose gate is connected to a signal input terminal TI and whose source is connected to a power supply voltage Vcc terminal, and whose gate is connected to a signal input terminal Tl and whose source is connected to a power supply voltage Vcc terminal. a second transistor Q of opposite conductivity type connected and having its drain connected to the signal output terminal To;
2, and third and fourth transistors Q3 . Q
4, the drain of the transistor Q3 is connected to the drain of the transistor Ql as an input terminal, and the drain of the transistor Q3 is connected to the drain of the transistor Ql.
The current mirror circuit 1 has a drain connected to a signal output terminal TO as an output terminal, and a current mirror circuit 1 in which the sources of transistors Qs and Q4 are both connected to a ground terminal.

In this example, in the positive half cycle of the input signal Vt,
The output current is supplied from transistor Q2, but at this time, transistor Q! The drain current of is the output current and the drain current of transistor Q4, and the input signal vlVc
Since transistor Q1 is forced into the off direction,
The drain current of transistor Q4 becomes small, so that the drain current of transistor Q2 becomes approximately equal to the output current.

Also, in the negative half cycle of the input signal Vl, the output current is supplied from the transistor Q4, but at this time, as the amplitude of the input signal vl increases, the drain current of the transistor Q1 also increases, and therefore the drain current of the transistor Q4 increases. This also increases the output current so that it can be supplied without shortage to meet the increase in output current, thereby preventing waveform distortion from occurring. Therefore, the drain current of the transistor Q4 when there is no signal can be suppressed to be smaller than when the input signal vl has a large amplitude.

Furthermore, since the drain current of the transistor Q4 is controlled by so-called negative feedback, no instability occurs.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

The difference between this embodiment and the first embodiment is that a fifth transistor Q5 of opposite conduction voltage has its gate connected to the signal input terminal TI and its drain connected to the power supply voltage Vcc terminal, and one end of this transistor Qs. A source follower circuit consisting of a constant current source circuit Io1 connected to the source and the colic connected to the ground terminal is provided, the gate of the first transistor Ql is connected to the source of the transistor Q6, and the first Example: For C, transistor Qh when there is no signal
The point is that the variation in current consumption due to the threshold voltage of Q- is reduced.

That is, the drain current of the transistor Q4 depends on the drain current of the transistor Q1, but the gate-source voltage of the transistor Q□ is determined approximately by the DC potential of the output terminal To and the power supply voltage Vcc, and the gate-source voltage of the transistors Qs and Qt. does not depend on

Therefore, it is insensitive to variations in the threshold voltages of the transistors Qs and Q1.

〔Effect of the invention〕

As explained above, the present invention includes a current mirror circuit including third and fourth transistors, a first transistor whose drain is connected to the input terminal of this current mirror circuit, and whose source is connected to the output terminal of this current mirror circuit. By adopting a configuration including a second transistor connected to the end, it is possible to prevent waveform distortion, reduce power consumption, and expand the range of application to integrated circuits. be.

Further, if the gate of the first transistor and the signal input terminal are connected via a source follower circuit composed of a fifth transistor and a constant current source circuit, then K
Therefore, the variation in the threshold voltage of the transistor K
This has the effect of eliminating variations in current consumption due to

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a first embodiment of the present invention, Fig. 2 is a circuit diagram showing a second embodiment of the present invention, and Fig. 3 is a circuit diagram showing an example of a conventional amplifier circuit. . 1...Current mirror circuit, Iol, Ioz
... Constant current source circuit b Qt~Qs...
transistor. Agent Patent Attorney Susumu Uchihara

Claims (2)

[Claims] (1) a first transistor of one conductivity type having a gate connected to a signal input terminal and a source connected to a first power supply voltage terminal; a gate connected to the signal input terminal and a drain connected to the first power supply voltage terminal; a second transistor of the opposite conductivity type, whose source is connected to the signal output terminal;
and a fourth transistor, the drain of the third transistor is connected as an input terminal to the drain of the first transistor, and the drain of the fourth transistor is connected as an output terminal to the signal output terminal. An amplifier circuit comprising: a current mirror circuit connecting a source of a fourth transistor to a second power supply voltage terminal. (2) a fifth transistor of opposite conductivity type whose gate is connected to the signal input terminal and whose drain is connected to the first power supply voltage terminal; one end is connected to the source of this fifth transistor and the other end is connected to the second transistor; 2. The amplifier circuit according to claim 1, further comprising a constant current source circuit connected to a power supply voltage terminal, and further comprising a gate of the first transistor connected to a source of the fifth transistor.