JPS60167513A - Equivalent resistance circuit - Google Patents

Abstract

PURPOSE:To set a desired resistance value with high accuracy regardless of characteristic parameters (beta0, W/L, etc.), by using an MOS transistor as an equivalent resistance. CONSTITUTION:Insulated gate type field effect transistors MOSFETQ1 and Q2 are constituted with the same conditions with substantially equal characteristic parameters (W/L, beta0, etc.). Therefore the working point of the FETQ2 is set at a point P when the gate-source voltage VGS3 is applied to a gate. Therefore the resistance value of the FETQ1 is substantially equal to that of the FETQ2 when viewed from the drain, i.e., a point Z'. Then the equivalent resistance of the desired value can be obtained regardless of the characteristic parameters W/L, beta0, etc. of both FETQ1 and Q2 by setting properly a constant current I0 and the reference voltage VREF. Then the point P can be set optionally by controlling at least one of the voltage VREF and the current I0. As a result, it is possible to control the impedance, i.e., the equivalent to a desired level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention is suitable for use in semiconductor integrated circuit devices (10), etc., and particularly relates to a technique for setting the resistance value of a resistor with extremely high accuracy.

[Background technology]

A diffused resistor is often used as the resistor used for the resistor 10, but a pinch resistor may be used if a high resistance value is essential. However, the pinch resistor has a problem in that the resistance value varies widely.

Further, as a method for forming a resistance, a MOSFET (insulated gate field effect transistor) is sometimes used to form an equivalent resistance. If this is used, the voltage applied to the gate will cause M
This has the advantage that the on-resistance of the OSFET can be controlled.

The present inventor uses MOSFET-g, which has a high resistance value,
We also considered creating a resistor whose resistance value can be varied. However, it has become clear that the equivalent resistance circuit described above has the following problems due to the characteristics of the MOS transistor.

MOS) When using a transistor as a variable resistor, use MOS
The operating region of the FET is the non-saturation region (straight region) shown in FIG. The non-saturation region of a MOS transistor is defined by the gate-source voltage VG and the threshold voltage Y
V, s drain-source voltage VVD, then l
V, 5-VTl > IVD, occurs when 1.

And the current ID8 between drain and source is as follows:
...(1) is found. In addition, (in equation 11, μn
is the electron surface mobility, 'ox is the dielectric constant of the oxide film, tox is the thickness of the oxide film, W is the channel width, L is the channel length,
vos, vT, and VD8 are as described above. By the way, the saturation region of the transistor (MOS) is 1G8"T
This occurs when I<IVD81, and the drain-source current ID8 is generated.

When using a MOS) transistor as a variable resistor,
As mentioned above, the MO8FET is operated in the unsaturated region, and in order to calculate the equivalent resistance value at this time, the equation (1) is partially differentiated by VD8.

tox I get Y.

That is, the resistance value R when used as a MOS) Ranjistake equivalent resistance is the value of vG81 vT, β. ,W/
It is also influenced by L, and these parameters are likely to have errors depending on the manufacturing process conditions of lO. For this reason, it has been extremely difficult to use MO8FETv as a highly accurate resistor.

[Object of the invention] The object of the present invention is to
The object of the present invention is to provide a circuit technology that allows the resistor to be used as a highly accurate resistor, regardless of parameters such as E T )'l, l'o -W/L-Vt, etc.

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

[Summary of the invention]

Summary of the invention disclosed in this application: Briefly stated,
It is as follows.

That is, the first MOS transistor Q supplies a reference voltage to the inverting input terminal of the operational amplifier 10, and its drain is connected to the non-inverting input terminal of the operational amplifier 1.
1, a constant current is supplied to the first MOS transistor (transistor) and this first MOS transistor by the output voltage of the operational amplifier.
By supplying a gate voltage to a second MOS transistor manufactured under substantially the same process conditions as the transistor, and using the second MOS transistor as an equivalent resistance, parameters such as β, W/L, etc. The object of the present invention is to set the desired resistance value Y with high accuracy regardless of the resistance value Y.

[Embodiment 1] An embodiment of an equivalent resistance circuit to which the present invention is applied will be described with reference to FIGS. 2 and 3Y. Note that FIG. 2 is a characteristic curve diagram showing the voltage/current characteristics of a MOS transistor, and FIG. 3 is a circuit diagram of an equivalent resistance circuit.

In FIG. 3, Qr -Q- is a MOSFET, which is constructed in the same semiconductor integrated circuit under the same process conditions. A constant current of 1° is supplied to the non-inverting input terminal t+l of the operational amplifier 1 and the drain of the MOS transistor Q through the constant tfi circuit O8.

This constant current l. ID8 of MQSFETQ+ is set.

10,000, the reference voltage vRI, F is supplied to the inverting input terminal (@) of the operational amplifier 1, and the non-inverting input terminal (F+ -) becomes the same potential as the reference voltage vRIF.This sets VDl+ of MO8FETQ.Then, point P is set as the operating point from the characteristic curve shown in Fig. 2.At this time, the Q of MOSFET, V.8
■. It becomes 83. In other words, V. 8° is output from the operational amplifier 1. In other words, the equivalent resistance of the transistor Q (i['&R1, RI
MO83 such that R1,y is obtained from the operational amplifier.

At this time, the resistance value seen from the drain of MO8FETQ is determined by the slope (θ) of the characteristic curve at point jP shown in FIG. -10,000V. s3 is stamped to the gate of the second MO8FETQ2. MO8FETQ,.

Since Q is configured under the same conditions and their respective characteristic parameters (W/L, β, etc.) are substantially the same, ■. 8
3 is applied to the gate, the operating point of MO8FETQ2 is also set to point P. Therefore, the resistance value seen from the drain, that is, from the point Z', is substantially the same as that of transistor Q2.

By setting the constant current IO and reference voltage ■R, eF in this way, the characteristic parameters W/L, β of MOS FET Q+ = Q2. An equivalent resistance of a desired resistance value can be obtained regardless of the resistance value. The operating point P is arbitrarily set by adjusting the voltage level of the reference voltage vREF and the amount of current 1o by at least 10,000 points, thereby reducing the impedance, that is, the equivalent resistance! It can be controlled to a desired value.

[Embodiment 2] Next, a second embodiment of the present invention will be explained with reference to FIG. In addition, in this example, the equivalent resistance? A plurality of MOS transistors are provided.

That is, when VG8 is set as described above for MO8) transistor Q1, MO8) transistor Q
2. V of Q, *, Q,. 8 is also set.

In this case, if MO8) transistor Q and Nikki W-10 are used, and the W/L values of MOS transistors Qg -Qs and Q4 are respectively set to 7110.20.30, then as seen from each drain of transistor Qt -Q= -Q4 The impedance Zinl + ``+n2 + '' iHa is obtained inversely proportional to the stone. Therefore, when obtaining a plurality of equivalent resistances, the single equivalent resistance circuit shown in this embodiment is very convenient.

[Embodiment 3] Next, as a third embodiment of the present invention, an application example of the equivalent resistance circuit will be described with reference to FIG.

A bypass filter 2 is provided between the amplifiers 11 and 12. The resistor R constituting the bypass filter 2 may be any of the MOS transistors Q, Q, Q, and the like. The low frequency of the input signal ■in supplied to the amplifier 11 is cut off by the bypass filter 2, and its cutoff frequency is equal to the reference voltage V as described in the first embodiment.
□2, or current l. can be controlled by

〔effect〕

(1) Multiple MOSs manufactured under the same manufacturing conditions
By setting the operating point of one of the transistors, the operating point of the other MO8) transistor can be set, so the equivalent resistance of the MO8) transistor can be obtained regardless of the characteristic parameter error during the manufacturing of the MOS transistor. This effect can be obtained.

Above, the invention made by the present inventor has been specifically explained based on each example. However, the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist of the invention. It goes without saying that something is true.

For example, the transistor Q, +*Qt e Qa
eQ4 is not limited to MOSFET,
It may also be a T-FET (junction type PET).

In addition, even if the reference voltage VRE F is configured to be variable, J
:1. ).

[Application field]

In the above description, the invention is mainly applied to an equivalent resistance circuit, which is the background of the invention made by the present inventor, but the present invention is not limited thereto.

For example, in addition to filter circuits, the present invention can be used in voltage control circuits and the like.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram 7 showing the operating range of MO8) transistor.
2 shows a characteristic diagram illustrating the operating point of the MO8 transistor that constitutes a part of the equivalent resistance circuit to which the present invention is applied, and FIG. 3 shows the equivalent resistance circuit according to the first embodiment of the present invention. FIG. 4 shows a circuit diagram of an equivalent resistance circuit according to a second embodiment of the present invention, and FIG. 5 shows a circuit diagram Z of a filter circuit according to a third embodiment of the present invention. 1... operational amplifier, Q, -O2-Qa, O4...
MOS) transistor, O8, ... constant current circuit, VRI
cF...Reference voltage, Zinl' Zin2+ "in
3"' impedance, 2...filter circuit, R...
・Resistance, Io...current, P...operating point. αB Figure 3 Figure 1 Figure 2

Claims (1)

[Claims] 1. A first field effect transistor (Q,), a second field effect transistor (Q,), and a constant current source (Os,) that supplies the drain current of the first field effect transistor (Q,). and an operational amplifier (1), supplying a reference voltage to the inverting input terminal of the operational amplifier (1), and connecting the positive phase input terminal of the operational amplifier (1) to the first
connected to the drain of the field effect transistor (Q,),
The output of the operational amplifier (1) is input to the first. An equivalent resistance circuit characterized in that it is supplied to the gates of the second field effect transistors (Q, , Q).