JPS61295709A - Operational amplifier - Google Patents

Abstract

PURPOSE:To obtain a differential amplifier which supplies both differential outputs to a final-stage amplification part and is driven by a low-voltage power source by compensating mutual input voltage ranges by suing the 1st differential amplification part which has a P type MOSFET as an input transistor (TR) and the 2nd differential amplification part which has an N type MOSFET as an input TR, and composing one output of those differential outputs while making the DC bias point of one output coincident with the output bias point potential of the other output by a level shifting means. CONSTITUTION:The output terminal 20 of the level shifter 14 is connected to the output terminal 19 of a differential amplifier 200 to send a gate signal to the MOSFET 9 of the final-stage amplification part. Here, the quantity of the voltage shifting of the level sifter 14 is set properly and the voltage level at its output terminal 20 is equalized to the voltage level at the output terminal 19 of the differential amplifier 200. This circuit uses N type MOSFETs 3 and 5 and P type MOSFETs 5 and 6 as respective input MOSFETs of the two differential amplification parts 100 and 200, so even when a low voltage source is used, an input voltage level to be used has a wide range from a low supply voltage VSS to a high supply voltage VDD.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a complementary MO
The present invention relates to an operational amplifier having a nine-transistor configuration.

[Summary of the Disclosure] The present invention provides an operational amplifier having a complementary MOS (MOS) transistor configuration, which includes a first differential amplifier section having an N-type MOSFET as an input transistor, and a second differential amplifier section having a P-type MOSFET as an input transistor. and a level shift means that is supplied with the output of one of the first and second differential amplifiers and shifts the bias voltage level, and the other of the first and second differential amplifiers. The two sets of differential amplifiers complement each other's input voltage ranges, so that the input voltage range is This invention discloses a technique that can realize an operational amplifier that can have a wide range of voltage and can be driven with a low voltage power supply.

Note that this summary is provided solely for the purpose of quickly accessing the technical content of the present invention, and does not have any influence on the technical scope of the present invention or the interpretation of rights.

[Prior art] Recently, C-DO, which has a simple process and low power consumption, has been developed.
Digital/analog circuits using S process technology are attracting attention, and operational amplifiers are often constructed with C-MOS transistors.

In such a conventional operational amplifier circuit, it has been proposed to provide an inverting level shifter with a gain of 1 in order to enable low voltage operation (for example, Institute of Electronics and Communication Engineers technical report CAS84-33).

In this circuit configuration, in order to drive the input MOSFET, the input voltage needs to be higher than the threshold voltage of the MOSFET. In other words, the input voltage is limited to a value within the range obtained by subtracting the threshold voltage of the MOSFET from the power supply voltage, and therefore, lowering the power supply voltage narrows the dynamic range, so from this point on, it is not possible to lower the power supply voltage. There was a problem.

[Problems to be Solved by the Invention] Therefore, the purpose of the present invention is to provide an operational amplifier that operates at a lower power supply voltage that could not be achieved with the conventional operational amplifier circuit configuration.

[Means for solving the problem] In order to achieve such an object, the present invention uses an N-type M
A first differential amplifier section that uses an OSFET as an input transistor, and a second differential amplifier section that uses a P 9 MOSFET as an input transistor.
a differential amplification section; a level shift means that is supplied with the output of one of the first and second differential amplification sections and shifts a bias voltage level; and the first and second differential amplification sections. An operational amplifier is configured by comprising a final stage amplification section which is supplied with the output of the other one of the two and a level-shifted signal from the level shift means.

[Created by Jli] According to the present invention, P,! ! ! A first differential amplifier section using a MOSFET as an input transistor and an N-type MOSFET
Using a second differential amplifier section with , as an input transistor,
Since the two input voltage ranges are complemented, and the DC bias point of one of these differential outputs is matched to the output bias point potential of the other using a level shift stage, both outputs are supplied to the final stage amplifier. can, therefore,
A differential amplifier that can be driven with a low voltage power supply can be realized.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

An embodiment of the operational amplifier of the present invention is shown in FIG.

In FIG. 1, 1 to 9 are MOSFETs, 11 to 13 are constant current sources, 14 is a level shifter, 15 and 18 are terminals that supply bias voltage, 17 and 18 are input terminal pairs, and 2
1 is the output terminal, 22.23 is the positive and negative power supply Voo, Vss
Each power line.

10 and 19 are output terminals of differential amplifier sections 100 and 200, respectively, and one output terminal IO is connected to the input terminal of level shifter 14. Reference numeral 20 is an output terminal of the level shifter 14, and this output terminal 20 is connected to the output terminal 19 of the differential amplifier section 200, and the output terminal 20 is connected to the output terminal 19 of the differential amplifier section 200.
Transfer the signal to the gate of OSFET 9. Here, the amount of voltage shift in the level shifter 14 is appropriately determined,
The voltage level of the output terminal 20 is made to be the same as the voltage level of the output terminal 18 of the differential amplifier section 200. In this circuit, N-type MOSFETs 3 and 4 are used as input MOSFETs for two sets of differential amplifiers 1.00 and 200.
Since P-type MOSFETs 5 and 6 are used, the input voltage range is wide even when using a low voltage power supply.

The reason for this will be explained using FIG. 2.

FIG. 2 shows a normal operational amplifier comprising a differential amplification section made up of MOSFETs 30 to 34 and a final stage amplification section made up of MOSFETs 35 and 3Et. here,
Each MO9FET requires a gate-source voltage equal to or higher than a threshold voltage (hereinafter referred to as vT). If the gate-source voltage is lower than VT)I, no effective current will flow.In other words, in order to drive the N-type input MOSFETs 32 and 33, the gate-source voltage of such MOSFETs must be
A minimum voltage of VyH or higher is required as the source-to-source voltage. Therefore, even in an ideal operational amplifier, the input voltage range is between the higher supply voltage (hereinafter referred to as V) and the lower supply supply voltage (hereinafter referred to as Vss) by VTH higher. limited to. That is, the input voltage level is limited to the range from (Vss+VTH) to WOO.

Furthermore, in an operational amplifier using a P-type input MOSFET, the input voltage level similarly varies from Vss to (V
oo -VTH).

As described above, the circuit of the present invention has an N-type input MO9FE
Since it has a differential amplifier section with T and a differential amplifier section with P-type input MOSFET, even if a low voltage power supply is used,
A wide range of input voltage levels from Vss to VOO can be used.

A specific embodiment of the operational amplifier according to the present invention is shown in FIG. In Figure 3, 40-57 is a MOSFET, 58
, 59 is a terminal for supplying a bias voltage, 80 and 61 are a pair of input terminals, 82 and 83 are output terminals of two sets of differential amplifiers 68 and 69, 64 is an output terminal of a level shifter 70, and 65 is a final stage amplifier This is an output terminal of the section 71.

Block 68 is a bias circuit that applies a bias voltage to the differential amplifier section 68; block 67 is a bias circuit that applies bias voltage to the differential amplifier section 69 and the final stage amplifier section 71;
Block 68 is an N-MOS differential amplifier using an N-type MO9FET as an input device, block 69 is a P-MOS differential amplifier using a P-type MOSFET as an input device, block 70 is a level shifter circuit, block 7
1 is a final stage amplification section.

Here, an input voltage is applied to each input terminal 60 and 61 of two sets of differential amplifiers 68 and 68, and the output of one of these differential amplifiers 6 and 69, in this example, N-M
The voltage at the output terminal 62 of the OS differential amplifier B8 is level-shifted by the level shifter circuit 70, and the level shift output 64 and the output of the other differential amplifier, in this embodiment, the P-MO3 differential amplifier 69, are It is set so that the output at the output terminal 63 has the same bias level.

In other words, either one of the differential amplifier sections 68 or 68
Even if this is removed, the DC input level of the final stage amplifier section 71 will not change. Therefore, the tree embodiment operational amplifier is
Although it has two sets of differential amplifier sections 68 and 68,
It operates in the same way as an operational amplifier having one set of differential amplification sections.

Next, a case will be described in which only one differential amplifier section is driven depending on the DC bias level or signal level of the input signal.

When the input voltage level is between (Voo VTH) and V, as already explained with respect to the circuit of FIG. Since it is more than VTH,
This differential amplification section 68 is being driven, so the differential amplification section 68 operates normally and transmits the signal to the level shifter circuit 70 and further to the final stage amplification section 71. At this time, in the differential amplifier section 68, the P-type MOSFET 5
0 and 51 have respective gate-source voltages below Vm and are not driven, so the voltage level at terminal 72 becomes below VTH. In other words, MOSFETs 51 and 53 are in an OFF state, that is, a high impedance state. Therefore, the output terminal 6 of the level shifter circuit 70
Level 4 operates only according to the input signals from P-type MOSFETs 48 and 47 without being affected by the input signals coming from P-type MOSFETs 50 and 51.

Conversely, when the input voltage is less than vTH, the differential amplifier 6
The circuit 9 operates normally and transmits its output to the final stage amplifier 71. At this time, in the differential amplifier section 68, the N-type MO
SFETs 4B and 47 have a gate φ source voltage of vT.
Since the voltage level of terminals 73 and 62 becomes higher than (Voo - VTH) and the MOS
FET 54 is turned off, and the input signal no longer propagates to output terminal 64 of level shifter circuit 70.

Therefore, in this case, the P-type MOSF of the differential amplifier section 68
Only input signals coming from ETs 50 and 51 are propagated to output terminal 65.

As is clear from the above, the operational amplifier shown in FIG. 3 has a high level of voltage gain over a wide input voltage range from Vss to VOO. As a result, if the low voltage power supply, that is, the power supply voltage satisfies 2vT1.1 or more, it is possible to achieve low voltage drive, which is highly desired in general application circuits.

Although the input MO3FET of the level shifter circuit 70 in FIG. 3 is a P-type MOSFET, it can be replaced with an N-type MOSFET.
It may also be an ET. However, in that case, a P-type MO9FET will be used as the input MO9FET of the final stage amplifier section 71.

[Effects of the Invention] According to the present invention, by using a first differential amplification section that uses a P-type MOSFET as an input transistor and a second differential amplification section that uses an N-type MOSFET as an input transistor, the mutual input voltage is Since the ranges are complemented and the DC bias point of one of these differential outputs is matched to the output bias point potential of the other by a level shift stage and combined, both outputs can be supplied to the final stage amplifier. , it is possible to provide an operational amplifier that can be driven with a low voltage power supply.

As an example, VDD is 2. When 0.8V is used as the process parameter for OL VTH, the input voltage range can be increased to approximately 2.2VI, whereas the conventional technology could only provide an input voltage range of 1.2VI. On the contrary, if the input range is kept at 1.2V, which is the same as in the conventional technology, the operational amplifier can be operated even if the drive power supply voltage is as low as 1.2V. .

Therefore, for application circuits that conventionally required a power supply consisting of two 1.5V dry batteries connected in series, the present invention can now be used with one 1.5V dry cell, resulting in significant equipment downsizing. It also has the advantage of being lightweight.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the configuration of an operational amplifier according to the present invention, FIG. 2 is a circuit diagram showing a general conventional operational amplifier, and FIG. 3 is a specific implementation of the operational amplifier according to the present invention. FIG. 2 is a circuit diagram showing an example configuration. 1.2, 7.8...MOSFET, 3.4...N type input MOSFET, 5.6...P
Type input MOSFET, 9...Final stage amplifier MOSF
ET, 1.0.19... Output terminal of differential amplifier section, 11.12
．． 13... Constant current source, 14... Level shifter, 15, le... Bias voltage supply terminal, 17.18.
... Input terminal pair, 20 ... Level shifter output terminal, 21 ... Output terminal, 22 ... Voltage V line, 23 ... Power supply Vss line.

Claims (1)

[Claims] 1) a first differential amplification section having an N-type MOSFET as an input transistor; a second differential amplification section having a P-type MOSFET as an input transistor; and the first and second differential amplification sections. level shifting means that is supplied with the output of one of them and shifts the level of the output; and supplied with the output of the other of the first and second differential amplifier sections and the output from the level shifting means. 1. An operational amplifier comprising: an amplifying section in which 2) The operational amplifier according to claim 1, wherein the positive side and negative side power supply arrangements of the first and second differential amplifier sections are complementary.