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US5684318A Expired / Lapsed US ⏱️ 0.0 years remaining

Electronic devices with thin-film circuit elements forming a sampling circuit

Assignee: US Philips Corp
•
Filing: 1996-04-25
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Granted: 1997-11-04
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Expires: 2016-04-25
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Abstract

Abstract In an LCD or other electronic device, thin-film circuit elements on a substrate (100) form a sample-and-hold or other sampling circuit (10). The circuit (10) comprises a TFT (Ts) as a sampling transistor and preferably another TFT (T2) to compensate for displacement currents in charging and discharging the insulated gate (12) of the sampling TFT. Even when T2 is included, a slow drift in output voltage (Vo) is observed when Ts switches off, and this limits use of the circuit, especially in large area active-matrix devices. In accordance with the invention this slow drift is removed or significantly reduced by injecting minority carriers into the channel region of Ts (and T2) from a doped opposite-type region (119) or Schottky contact region (119) which is forward biased via a thin-film supply line (129). The minority carriers neutralise majority carriers which are being slowly released by thermal emission from trapping states in the TFT body.

Inventors

  • 👤 John R. A. Ayres
  • 👤 Martin J. Edwards

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-05 15:27
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/60; H10D30/67; H10D30/6757; G; G09; G09G; G09G3/00; G09G3/20; G09G3/34; G09G3/36; G09G3/3611; G09G3/3685; G09G3/3688; H10D30/6704; H10D30/6713; H10D86/00; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/1333; G02F1/1345; G02F1/13454; G09G2310/00; G09G2310/02; G09G2310/0264; G09G2310/0294

Claims Analysis

Total Claims: 14
Claim 1
Independent Claim 282 words
An electronic device comprising a pattern of thin-film circuit elements on a substrate which form a sampling circuit of the device, the circuit comprising a sampling transistor between an input node and an output node, said sampling transistor being a thin-film field-effect transistor element having an insulated gate adjacent to a semiconductor thin-film body which is deposited on the substrate and comprises a channel region of the transistor controlled by the insulated gate, the gate being connected to a thin-film control line for switching the transistor on and off so as to sample a signal from the input node and to pass the sampled signal to the output node, the passage of the signal by the transistor in an on state being effected by a flow of charge carriers of a first conductivity type which are majority charge carriers of the channel region, the channel region having a density of trapping states which trap charge carriers of the first conductivity type in the on state of the transistor, and which release the trapped charge carriers of the first conductivity type by thermal emission when the transistor is switched into an off state, the sampling transistor comprising a minority charge carrier injector region which is adjacent the channel region and is connected to a thin-film supply line for forward biasing the injector region with respect to the channel region to provide a supply of charge carriers of a second conductivity type opposite to the first type for injection as minority charge carriers into the channel region during switching off of the transistor, which minority charge carriers neutralize within the channel region the charge carriers of the first conductivity type released by thermal emission.
Claim 2
Dependent Claim 282 words
An electronic device comprising a pattern of thin-film circuit elements on a substrate which form a sampling circuit of the device, the circuit comprising a sampling transistor between an input node and an output node, said sampling transistor being a thin-film field-effect transistor element having an insulated gate adjacent to a semiconductor thin-film body which is deposited on the substrate and comprises a channel region of the transistor controlled by the insulated gate, the gate being connected to a thin-film control line for switching the transistor on and off so as to sample a signal from the input node and to pass the sampled signal to the output node, the passage of the signal by the transistor in an on state being effected by a flow of charge carriers of a first conductivity type which are majority charge carriers of the channel region, the channel region having a density of trapping states which trap charge carriers of the first conductivity type in the on state of the transistor, and which release the trapped charge carriers of the first conductivity type by thermal emission when the transistor is switched into an off state, the sampling transistor comprising a minority charge carrier injector region which is adjacent the channel region and is connected to a thin-film supply line for forward biasing the injector region with respect to the channel region to provide a supply of charge carriers of a second conductivity type opposite to the first type for injection as minority charge carriers into the channel region during switching off of the transistor, which minority charge carriers neutralize within the channel region the charge carriers of the first conductivity type released by thermal emission.
Claim 3
Dependent Claim 45 words
A device as claimed in claim 1, wherein the sampling transistor comprises semiconductor source and drain regions of the first conductivity type which are coupled to the input and output nodes respectively, and the injector region is a semiconductor region of the second conductivity type.
Claim 4
Dependent Claim 46 words
A device as claimed in claim 2, wherein the semiconductor thin-film which provides the body of the sampling transistor has a region which is doped with conductivity type determining dopant characteristic of the second conductivity type to form the injector region of the second conductivity type.
Claim 5
Dependent Claim 29 words
A device as claimed in claim 2, wherein the region of the semiconductor thin film which comprises the channel region is sandwiched between the substrate and the insulated gate.
Claim 6
Dependent Claim 42 words
A device as claimed in claim 3, wherein a doped region of the second conductivity type protrudes to one side of the channel region to form both the injector region and at least a part of its connection to the supply line.
Claim 7
Dependent Claim 47 words
A device as claimed in claim 4, wherein the injector region is a doped region of the second conductivity type which is located adjacent to the upper surface of the semiconductor thin-film body and over at least one of the source and drain regions of the transistor.
Claim 8
Dependent Claim 57 words
A device as claimed in claim 3, wherein the insulated gate is sandwiched between the substrate and the semiconductor thin-film body, and the injector region is a doped region of the second conductivity type which is located adjacent to the upper surface of the semiconductor thin-film body and over at least a part of the channel region.
Claim 9
Dependent Claim 27 words
A device as claimed in claim 1 the sampling circuit is a sample-and-hold circuit comprising a charge-storage means coupled to the output node of the sampling transistor.
Claim 10
Dependent Claim 93 words
A device as claimed in claim 8, wherein the sample-and-hold circuit comprises a second thin-film field effect transistor whose gate charging and discharging characteristics when switching on and off are substantially the same as those of the sampling transistor, the second transistor has source and drain regions connected together and in series between the charge-storage means and the output node of the sampling transistor, and the gate of the second transistor is connected to a thin-film control line supplying a control signal complementary to that supplied to the gate of the sampling transistor.
Claim 11
Dependent Claim 45 words
A device as claimed in claim 9, wherein the second transistor includes a minority charge-carrier injector region for injecting minority charge-carriers into the channel region of the second transistor during the switching off of the second transistor when the sampling transistor is being switched on.
Claim 12
Dependent Claim 40 words
A device as claimed in claim 8, further comprising a plurality of the sample-and-hold circuits integrated on the same substrate with a plurality of cells, and in that the sample-and-hold circuits supply their sampled signals as information to the cells.
Claim 13
Dependent Claim 62 words
A device as claimed in claim 11, wherein the cells are organized in a matrix which has thin-film row lines for addressing rows of the matrix and has thin-film column lines for supplying the sampled signals to cells in the addressed row, and a drive circuit for the column lines comprises an individual one of the sample-and-hold circuits for each column line.
Claim 14
Dependent Claim 25 words
A device as claimed in claim 1, wherein the injector region of the sampling transistor is connected to ground potential by the thin-film supply line.

References Cited (Backward Citations)

US3660732A Cited
US4425631A Cited
US4870399A Cited
EP0342925A2 Cited
JPH0377922A Cited
JPH0377915A Cited
US5313075A Cited
US5300448A Cited
US5378911A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 2000-11-03 2001-05-05 2001-11-04 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 2004-11-03 2005-05-05 2005-11-04 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 2008-11-03 2009-05-05 2009-11-04 $7700.00 Window Closed / Lapsed

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