Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1975-03-21
1976-02-24
Miller, Charles D.
Communications: electrical
Audible indication
Percussion-type sound producer
H03K 1304
Patent
active
039407608
ABSTRACT:
A digital-to-analog converter of the type formed with a plurality of current source transistors arranged to carry different levels of current according to a predetermined weighting pattern, e.g., a binary weighting pattern. In the converter, a plurality of identically sized current source transistors carry the different levels of current and thus operate at different current densities with different base-to-emitter voltages subject to temperature drift. Stable emitter voltages, providing accurate levels of weighted current, are developed by means of resistances between the bases of successive current source transistors and a current source for developing across the interbase resistances a voltage linearly varying with absolute temperature, corresponding to the difference between base-to-emitter voltages of the successive current source transistors.
The apparatus for generating a current linearly varying with absolute temperature is formed with first and second transistors forced to carry the same current at different current densities to produce different base-to-emitter voltages, and means such as an emitter resistor responsive to the difference in the base-to-emitter voltages for developing a current, corresponding to the difference in base-to-emitter voltages, which varies linearly with temperature.
REFERENCES:
patent: 3594780 (1971-07-01), Greefkes
patent: 3633005 (1972-01-01), Leighton
patent: 3747088 (1973-01-01), Pastoriza
patent: 3842412 (1974-10-01), Spofford
patent: 3857021 (1974-12-01), Wilensky
Analog Devices Inc.
Miller Charles D.
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