Patent EP0629003A1 successfully refreshed from Google Patents.
EP0629003A1
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EP
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Electronic devices with thin-film circuit elements forming a sampling circuit
Assignee: Philips Electronics UK Ltd
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Filing: 1994-05-18
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Granted: —
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Expires: 2014-05-18
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 (121) 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 Richard Alan Ayres
- 👤 Martin John Edwards
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 19:12
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: 13
Claim 1
Independent Claim
208 words
An electronic device comprising on a substrate a pattern of thin-film circuit elements which form a sampling circuit of the device, the circuit comprising a sampling transistor between an input node and an output node, which sampling transistor is a thin-film field-effect transistor element having an insulated gate adjacent to a semiconductor thin-film body which accommodates a channel region of the transistor under the control of 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 being by a flow of charge-carriers of a first conductivity type which are majority charge-carriers of the channel region, which device is characterised in that the sampling transistor comprises a minority charge-carrier injector region in the vicinity of the channel region, which injector region is connected to a thin-film supply line for forward-biasing the injector region with respect to the channel region and so providing 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 the switching off of the transistor.
Claim 2
Dependent Claim
48 words
A device as claimed in claim 1, further characterised in that 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 3
Dependent Claim
49 words
A device as claimed in claim 2, further characterised in that 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 4
Dependent Claim
35 words
A device as claimed in claim 2 or claim 3, further characterised in that the region of the semiconductor thin film which accommodates the channel region is sandwiched between the substrate and the insulated gate.
Claim 5
Dependent Claim
48 words
A device as claimed in claim 3 or claim 4, further characterised in that 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 6
Dependent Claim
50 words
A device as claimed in claim 4, further characterised in that 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 7
Dependent Claim
60 words
A device as claimed in claim 3, further characterised in that 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 8
Independent Claim
35 words
A device as claimed in any one of the preceding claims, further characterised in that the sampling circuit is a sample-and-hold circuit comprising a charge-storage means coupled to the output node of the sampling transistor.
Claim 9
Dependent Claim
96 words
A device as claimed in claim 8, further characterised in that 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 10
Dependent Claim
48 words
A device as claimed in claim 9, further characterised in that 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 11
Independent Claim
47 words
A device as claimed in any one of claims 8 to 10, further characterised by 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 12
Dependent Claim
74 words
A device (particularly, but not exclusively, a liquid-crystal display) as claimed in claim 11, further characterised in that the cells are organised 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 in that a drive circuit for the column lines comprises an individual one of the sample-and-hold circuits for each column line.
Claim 13
Independent Claim
32 words
A device as claimed in any one of the preceding claims, further characterised in that the injector region of the sampling transistor is connected to ground potential by the thin-film supply line.
References Cited (Backward Citations)
FR2496342A1
Cited
JPS6294986A
Cited
US4870399A
Cited
EP0342925A2
Cited
JPH0377922A
Cited
JPH0377915A
Cited
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