US4857769A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Threshold voltage fluctuation compensation circuit for FETS
Assignee: Hitachi Ltd
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Filing: 1988-01-13
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Granted: 1989-08-15
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Expires: 2008-01-13
Abstract
Abstract This invention relates to a threshold voltage detection circuit for detecting the threshold voltage of field effect transistors (FETs) and to a semiconductor circuit capable of a stable operation irrespective of the fluctuation of the threshold voltage by utilizing this threshold voltage detection circuit. The source-drain path of first FET is connected in series with that of second FET having substantially the same threshold voltage as that of the first FET and the conductances of these first and second FETs are set to a predetermined ratio to generate a voltage drop associated with the threshold voltage in the first FET. This voltage drop can be used for detecting the threshold voltage and for level-shifting. The output of the series connection of the first and second FETs is applied to the gate of a constant current FET having the same threshold voltage as that of the first and second FETs and the drain current of the constant current FET can thus be set irrespective of the fluctuation of the threshold voltage.
Inventors
- 👤 Nobuo Kotera
- 👤 Kiichi Yamashita
- 👤 Taizo Kinoshita
- 👤 Hirotoshi Tanaka
- 👤 Satoshi Tanaka
- 👤 Minoru Nagata
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 12:48
CPC Classifications
H; H03; H03K; H03K19/00; H03K19/003; H03K19/00369; H03K19/00384
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
199 words
A semiconductor circuit comprising: (1) a plurality of first FETs having source-drain paths thereof connected in series; and (2) at least one second FET having the same conductivity type as that of said plurality of first FETs and substantially the same threshold voltage as that of said plurality of first FETs, and having the source-drain path thereof connected in series to the source-drain paths of said plurality of first FETs, wherein said plurality of first FETs operate in their linear region, the gates and drains of each of said first FETs being respectively connected electrically, wherein said second FET operates in its saturation region, the gate and source of said second FET being connected electrically wherein a voltage associated with said threshold voltage can be obtained between the drain and source of said first FETs when the conductances of said first FETs and that of said second FET are set to a predetermined ratio, wherein said first and second FETs are depletion mode FETs, and wherein said conductance ratio of said first and second FETs is set so that said voltage obtained between the drain and source of said first FETs is a predetermined multiple of said threshold voltage.
Claim 2
Dependent Claim
199 words
A semiconductor circuit comprising: (1) a plurality of first FETs having source-drain paths thereof connected in series; and (2) at least one second FET having the same conductivity type as that of said plurality of first FETs and substantially the same threshold voltage as that of said plurality of first FETs, and having the source-drain path thereof connected in series to the source-drain paths of said plurality of first FETs, wherein said plurality of first FETs operate in their linear region, the gates and drains of each of said first FETs being respectively connected electrically, wherein said second FET operates in its saturation region, the gate and source of said second FET being connected electrically wherein a voltage associated with said threshold voltage can be obtained between the drain and source of said first FETs when the conductances of said first FETs and that of said second FET are set to a predetermined ratio, wherein said first and second FETs are depletion mode FETs, and wherein said conductance ratio of said first and second FETs is set so that said voltage obtained between the drain and source of said first FETs is a predetermined multiple of said threshold voltage.
Claim 3
Dependent Claim
37 words
A semiconductor circuit according to claim 1, wherein the total number of said first FETs is set to a value which prevents a forward current from flowing through the gates of a plurality of said first FETs.
Claim 4
Dependent Claim
18 words
A semiconductor circuit according to claim 2, wherein said first and second FETs are N-channel depletion mode FETs.
Claim 5
Dependent Claim
133 words
A semiconductor circuit comprising: (1) a first FET; and (2) a second FET having the same conductivity type as that of said first FET and substantially the same threshold voltage as that of said first FET, and having its source-drain path connected in series with that of said first FET; wherein said first FET operates in its saturation region, the gate and drain of said first FET being connected electrically; wherein said second FET operates in its saturation region, a control voltage being applied between the gate and source of said second FET; and wherein a voltage associated with said threshold voltage can be obtained between the drain and source of said first FET when the conductance of said first FET and that of said second FET are set to a predetermined ratio.
Claim 6
Dependent Claim
133 words
A semiconductor circuit comprising: (1) a first FET; and (2) a second FET having the same conductivity type as that of said first FET and substantially the same threshold voltage as that of said first FET, and having its source-drain path connected in series with that of said first FET; wherein said first FET operates in its saturation region, the gate and drain of said first FET being connected electrically; wherein said second FET operates in its saturation region, a control voltage being applied between the gate and source of said second FET; and wherein a voltage associated with said threshold voltage can be obtained between the drain and source of said first FET when the conductance of said first FET and that of said second FET are set to a predetermined ratio.
Claim 7
Dependent Claim
17 words
A semiconductor circuit according to claim 4, wherein said first and second FETs are enhancement mode FETs.
Claim 8
Dependent Claim
41 words
A semiconductor circuit according to claim 5, wherein said conductance ratio of said first and second FETs is set so that said voltage obtained between the drain and souce of said first FET is a predetermined multiple of said threshold voltage.
Claim 9
Dependent Claim
307 words
A source-follower circuit comprising: (1) a plurality of first FETs having source-drain paths thereof connected in series; (2) a second FET having the same conductivity type as that of said first FETs and substantially the same threshold voltage as that of said first FETs; (3) a third FET having the same conductivity type as that of said first FETs and substantially the same threshold voltage as that of said first FETs, wherein the drain of said third FET is connected to a first operating potential point, an input voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of one of said FETs, wherein the source of one of said first FETs is connected to an output node and to the drain of said second FET, wherein said first FETs operate in their linear region, their gate and drains being connected electrically, wherein said second FET operates in its saturation region, its gate and source being connected electrically, wherein said third FET operates in its saturation region, wherein the following level shift voltage associated with said threshold voltage -V th develops between the gate and source of said first FETs when the conductance K 1 of said first FETs and the conductance K 2 of said second FET is set to a predetermined ratio β=K 2 /K 1 : V.sub.GS1 =-V.sub.th +V.sub.th (√β+1) wherein the conductance of said third FET and that of said second FET are set to a substantially equal value, wherein said first, second and third FETs are depletion mode FETs, and wherein the conductances of said first and second FETs are set to said ratio so that said level shift voltage obtained between the drain and source of said first FETs is a predetermined multiple of said threshold voltage.
Claim 10
Dependent Claim
307 words
A source-follower circuit comprising: (1) a plurality of first FETs having source-drain paths thereof connected in series; (2) a second FET having the same conductivity type as that of said first FETs and substantially the same threshold voltage as that of said first FETs; (3) a third FET having the same conductivity type as that of said first FETs and substantially the same threshold voltage as that of said first FETs, wherein the drain of said third FET is connected to a first operating potential point, an input voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of one of said FETs, wherein the source of one of said first FETs is connected to an output node and to the drain of said second FET, wherein said first FETs operate in their linear region, their gate and drains being connected electrically, wherein said second FET operates in its saturation region, its gate and source being connected electrically, wherein said third FET operates in its saturation region, wherein the following level shift voltage associated with said threshold voltage -V th develops between the gate and source of said first FETs when the conductance K 1 of said first FETs and the conductance K 2 of said second FET is set to a predetermined ratio β=K 2 /K 1 : V.sub.GS1 =-V.sub.th +V.sub.th (√β+1) wherein the conductance of said third FET and that of said second FET are set to a substantially equal value, wherein said first, second and third FETs are depletion mode FETs, and wherein the conductances of said first and second FETs are set to said ratio so that said level shift voltage obtained between the drain and source of said first FETs is a predetermined multiple of said threshold voltage.
Claim 11
Dependent Claim
294 words
A semiconductor circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and substantially the same threshold voltage as that of said first FET; (3) a third FET having the same conductivity type as that of said first FET and substantially the same threshold voltage of said first FET; (4) constant voltage generation means for generating a constant voltage kept substantially stable from the output terminal thereof, having one and the other ends thereof connected to first and second operating potential points, respectively; and (5) a constant current FET having the same conductivity type as that of said first FET and substantially the same threshold voltage as that of said first FET, and having its source connected to said second operating potential point; wherein the drain of said third FET is connected to said first operating potential point, said constant voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of said first FET; wherein the source of said first FET is connected to the gate of said constant current FET and to the drain of said second FET; wherein the source of said second FET is connected to said second operating potential point; wherein said first FET operates in its linear region, its gate and drain being connected electrically; wherein said second FET operates in its saturation region, its gate and source being connected electrically; wherein said third FET operates in its saturation region; and wherein the conductances of said first, second and third FETs are set so that the current flowing through the drain of said constant current FET is set substantially irrespective of said threshold voltage.
Claim 12
Dependent Claim
294 words
A semiconductor circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and substantially the same threshold voltage as that of said first FET; (3) a third FET having the same conductivity type as that of said first FET and substantially the same threshold voltage of said first FET; (4) constant voltage generation means for generating a constant voltage kept substantially stable from the output terminal thereof, having one and the other ends thereof connected to first and second operating potential points, respectively; and (5) a constant current FET having the same conductivity type as that of said first FET and substantially the same threshold voltage as that of said first FET, and having its source connected to said second operating potential point; wherein the drain of said third FET is connected to said first operating potential point, said constant voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of said first FET; wherein the source of said first FET is connected to the gate of said constant current FET and to the drain of said second FET; wherein the source of said second FET is connected to said second operating potential point; wherein said first FET operates in its linear region, its gate and drain being connected electrically; wherein said second FET operates in its saturation region, its gate and source being connected electrically; wherein said third FET operates in its saturation region; and wherein the conductances of said first, second and third FETs are set so that the current flowing through the drain of said constant current FET is set substantially irrespective of said threshold voltage.
Claim 13
Dependent Claim
27 words
A semiconductor circuit according to claim 8, wherein the conductance of said third FET and that of said second FET are set to a substantially equal value.
Claim 14
Dependent Claim
23 words
A semiconductor circuit according to claim 9, wherein said first, second and third FETs and said constant current FET are depletion mode FETs.
Claim 15
Dependent Claim
43 words
A semiconductor circuit according to claim 10, wherein said conductance ratio of said first and second FETs is set so that the level shift voltage obtained between the drain and source of said first FET is a predetermined multiple of said threshold voltage.
Claim 16
Dependent Claim
64 words
A semiconductor circuit according to claim 11, wherein the following level shift voltage associated with said threshold voltage -V th is generated between the gate and source of said first FET when the conductance K 1 of said first FET and the conductance K 2 of said second FET are set to a predetermined ratio β=K 2 /K 1 : V.sub.GS1 =V.sub.th +V.sub.th (√β+1)
Claim 17
Dependent Claim
247 words
A source-follower circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (3) a third FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; wherein the drain of said third FET is connected to a first operating potential point, an input voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of said first FET; wherein the souce of said first FET is connected to an output node and to the drain of said second FET; wherein the source of said second FET is connected to a second operating potential point; wherein said first FET operates in its saturation region, its gate and drain being connected electrically; wherein said second FET operates in its saturation region, a control voltage V c being applied to its gate and source; wherein said third FET operates in its saturation region; and wherein the following level shift voltage associated with said threshold voltage V th occurs between the gate and source of said first FET when the conductance K 1 of said first FET and the conductance K 2 of said second FET is set to a predetermined ratio β=K 2 /K 1 : V.sub.GS1 =√V.sub.c +(1-√β)V.sub.th
Claim 18
Dependent Claim
247 words
A source-follower circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (3) a third FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; wherein the drain of said third FET is connected to a first operating potential point, an input voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of said first FET; wherein the souce of said first FET is connected to an output node and to the drain of said second FET; wherein the source of said second FET is connected to a second operating potential point; wherein said first FET operates in its saturation region, its gate and drain being connected electrically; wherein said second FET operates in its saturation region, a control voltage V c being applied to its gate and source; wherein said third FET operates in its saturation region; and wherein the following level shift voltage associated with said threshold voltage V th occurs between the gate and source of said first FET when the conductance K 1 of said first FET and the conductance K 2 of said second FET is set to a predetermined ratio β=K 2 /K 1 : V.sub.GS1 =√V.sub.c +(1-√β)V.sub.th
Claim 19
Dependent Claim
27 words
A source-follower circuit according to claim 13, wherein the conductance of said third FET is set to a substantially equal value to that of said second FET.
Claim 20
Dependent Claim
18 words
A source-follower circuit according to claim 14, wherein said first, second and thid FETs are enhancement mode FETs.
Claim 21
Dependent Claim
42 words
A source-follower circuit according to claim 14, wherein said conductance ratio of said first and second FETs is set so that the level shift voltage obtained between the drain and source of said first FET is some multiples of said threshold voltage.
Claim 22
Dependent Claim
302 words
A semiconductor circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (3) a third FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (4) constant voltage generation means for generating a constant voltage kept substantially stable from the output terminal thereof, having one and the other end thereof connected to first and second operating potential points, respectively; and (5) a constant current FET having the same conductivity type as that of said first FET, having substantially the same threshold voltage as that of said first FET and having the source thereof connected to said second operating potential point; wherein the drain of said third FET is connected to said first operating potential point, said constant voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of said first FET; wherein the source of said first FET is connected to the gate of said constant current FET and to the drain of said second FET; wherein the source of said second FET is connected to said second operating potential point; wherein said first FET operates in its saturation region, its gate and drain being connected electrically; wherein said second FET operates in its saturation region, a control voltage being applied between its gate and source; wherein said third FET operates in its saturation region; and wherein the conductances of said first, second and third FETs are set so that the current flowing through the drain of said constant current FET is set substantially irrespective of said threshold voltage.
Claim 23
Dependent Claim
302 words
A semiconductor circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (3) a third FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (4) constant voltage generation means for generating a constant voltage kept substantially stable from the output terminal thereof, having one and the other end thereof connected to first and second operating potential points, respectively; and (5) a constant current FET having the same conductivity type as that of said first FET, having substantially the same threshold voltage as that of said first FET and having the source thereof connected to said second operating potential point; wherein the drain of said third FET is connected to said first operating potential point, said constant voltage is applied to the gate of said third FET and the source of said third FET is connected to the gate and drain of said first FET; wherein the source of said first FET is connected to the gate of said constant current FET and to the drain of said second FET; wherein the source of said second FET is connected to said second operating potential point; wherein said first FET operates in its saturation region, its gate and drain being connected electrically; wherein said second FET operates in its saturation region, a control voltage being applied between its gate and source; wherein said third FET operates in its saturation region; and wherein the conductances of said first, second and third FETs are set so that the current flowing through the drain of said constant current FET is set substantially irrespective of said threshold voltage.
Claim 24
Dependent Claim
27 words
A semiconductor circuit according to claim 17, wherein the conductance of said third FET is set to a value substantially equal to that of said second FET.
Claim 25
Dependent Claim
23 words
A semiconductor circuit according to claim 18, wherein said first, second and third FETs and said constant current FET are enhancement mode FETs.
Claim 26
Dependent Claim
42 words
A semiconductor circuit according to claim 19, wherein said conductance ratio of said first and second FETs is set so that the level shift voltage obtained between the drain and source of said first FET is some multiples of said threshold voltage.
Claim 27
Dependent Claim
250 words
A semiconductor circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (3) constant voltage generation means for generating a constant voltage kept substantially stable from the output terminal thereof, having one and the other end thereof connected to first and second and second operating potential points, respectively; and (4) a constant current FET having the same conductivity type as that of said first FET, having substantially the same threshold voltage as that of said first FET and having the source thereof connected to said second operating potential point; wherein the drain of said first FET is connected to said first operating potential point, said constant voltage is applied to the gate of said first FET and the source of said first FET is connected to the gate of said constant current FET and to the drain of said second FET; wherein the source of said second FET is connected to said second operating potential point; wherein said first FET operates in its saturation region, said constant voltage being aplied to the gate of said first FET; wherein said second FET operates in its saturation region, its gate and source being connected electrically; and wherein the conductances of said first and second FETs are set so that the current flowing through the drain of said constant current FET is set substantially irrespective of said threshold voltage.
Claim 28
Dependent Claim
250 words
A semiconductor circuit comprising: (1) a first FET; (2) a second FET having the same conductivity type as that of said first FET and having substantially the same threshold voltage as that of said first FET; (3) constant voltage generation means for generating a constant voltage kept substantially stable from the output terminal thereof, having one and the other end thereof connected to first and second and second operating potential points, respectively; and (4) a constant current FET having the same conductivity type as that of said first FET, having substantially the same threshold voltage as that of said first FET and having the source thereof connected to said second operating potential point; wherein the drain of said first FET is connected to said first operating potential point, said constant voltage is applied to the gate of said first FET and the source of said first FET is connected to the gate of said constant current FET and to the drain of said second FET; wherein the source of said second FET is connected to said second operating potential point; wherein said first FET operates in its saturation region, said constant voltage being aplied to the gate of said first FET; wherein said second FET operates in its saturation region, its gate and source being connected electrically; and wherein the conductances of said first and second FETs are set so that the current flowing through the drain of said constant current FET is set substantially irrespective of said threshold voltage.
Claim 29
Dependent Claim
17 words
A semiconductor circuit according to claim 21, wherein said first and second FETs are depletion mode FETs.
Claim 30
Dependent Claim
41 words
A semiconductor circuit according to claim 22, wherein said conductance ratio between said first and second FETs is set so that the voltage obtained between the drain and source of said first FET is a predetermined multiple of said threshold voltage.
References Cited (Backward Citations)
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