Electrical transmission or interconnection systems – Nonlinear reactor systems – Parametrons
Patent
1984-10-18
1986-07-08
Clawson, Jr., Joseph E.
Electrical transmission or interconnection systems
Nonlinear reactor systems
Parametrons
357 55, 357 59, 307252A, 307252J, 307252N, 307305, H01L 2974
Patent
active
045996334
DESCRIPTION:
BRIEF SUMMARY
The invention relates to structures of the self-firing "thyristor" kind.
In the patent application filed on Nov. 25, 1982 under the No. 82 19728 for "Intrinsic firing thyristor structure and application thereof to the construction of a bidirectional device", intrinsic self-firing thyristor structures were described, that is to say which are triggered off at zero voltage under the effect of the internal displacement current CdV/dt alone, this self-firing being inhibited by a gate-cathode short-circuit and the advantages thereof were mentioned.
These intrinsic self-firing structures comprise successive semiconductor layers forming a first emitter region (preferably of N type), a first base region, or inhibition base (preferably of P type), a second base region (main base, preferably of N type) and a second emitter region (preferably of P type), the first emitter region having at least one cathode contact, the first base region being connected to at least one inhibition gate contact, the second emitter region having an anode contact, and at least one switch means adapted for creating a short-circuit between the inhibition gate and the cathode and thus to inhibit the self-firing faculty of the thyristor and are characterized in that said base and emitter regions are formed so as to constitute a very high sensitivity thyristor.
To this end, the thicknesses and doping of the first emitter and base regions are chosen so that the intrinsic gain of the first NPN transistor is high at low level and passivation of the junctions is particularly taken care of, in accordance with the information given in patent No. 82 19728.
Since it has proved very difficult to produce "intrinsic" self-firing structures on an industrial scale, self-firing was then initialized by means of a small admittance (an assisting resistance of a few megohms, or a capacitor of the order of 10 nF or so).
When these self-firing structures are assisted by a capacitor, the firing time is greatly reduced with respect to assistance by resistor, so that the control thereof by an MOS transistor, which has been contemplated and has proved very practical in application to static relays, becomes difficult because of the time constant for charging the gate of the MOS. On the other hand, when said structures are assisted by resistance, the assistance current does not exceed a few microamps and it is very localized, which limits the possibilities of switching high currents.
If the gate area is increased, the density of the assisting current becomes low and the assistance inefficient.
The present invention proposes overcoming this problem by means of an amplifying gate structure comprising an assisted thyristor, of small size and of very high sensitivity which then becomes the pilot for a main transistor itself having a very high sensitivity.
In this amplifying gate structure, the high sensitivity is however not sufficient for obtaining "intrinsic" selfiring, i.e. without an assisting admittance.
The main aim of the invention is to provide such an amplifying gate structure of integrated type, which has particular advantages. It will be noted that such a structure, despite its similarities with known amplifying gate thyristor structures, is radically distinguished therefrom by its operation, due to its characteristics and its method of control.
According to a first characteristic of the invention, the main thyristor of said amplifying gate structure is of the "mesa" type, whereas the pilot thyristor is formed by a small-sized central portion of the "mesa" structure, and is defined by the "planar" technique, with absence of edge effect, the main base of the pilot thyristor being isolated from that of the main thyristor, contrary to the known structure of an amplifying gate thyristor, the amplifying gate structure of the invention being further characterized, with respect to said known structure, in that control thereof is provided by a gate-cathode short-circuit of the pilot and main thyristors, in that the main thyristor has its own gate and a high sensitivity a
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Souques Georges
Thire Jacques
Clawson Jr. Joseph E.
Drucker William A.
La Telemecanique Electrique
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