Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By amplitude
Patent
1998-01-13
1999-11-09
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By amplitude
327541, 327538, 323312, 323313, H03F 345, G05F 110
Patent
active
059822015
ABSTRACT:
A low voltage CTAT current source includes a bipolar transistor connected across two series-connected resistors. A voltage developed across the resistors turns on the transistor, making the current through the resistors CTAT. A second transistor supplies the resistor current; its base (if bipolar) is connected to the node between the resistors, which are selected to limit the transistor's base-collector forward bias and collector-emitter voltage to a preselected fraction of the first transistor's V.sub.be, allowing the CTAT current source to operate with supply voltages of less than two junction voltage drops. A PTAT current can be combined with the CTAT current to create a temperature-compensated current. A low voltage current mirror has the respective bases of a pair of cascoded transistors connected across a resistor which is also connected between the bottom transistor's collector and a programming current. When the transistors are matched, the top transistor's collector-emitter voltage about equals the voltage across the resistor, which is selected to establish a V.sub.ce just high enough to avoid saturation and allow the circuit to operate with only two unsaturating V.sub.ce 's of headroom. The current mirror's lower headroom requirements are advantageously employed in a low voltage differential to single-ended converter circuit, and the current mirror and CTAT current source can be combined in numerous analog circuits to enable their operation at lower supply voltages.
REFERENCES:
patent: 4680483 (1987-07-01), Giordance
patent: 5200654 (1993-04-01), Archer
patent: 5349285 (1994-09-01), Okanobu
patent: 5485074 (1996-01-01), Tomasini et al.
patent: 5828329 (1998-10-01), Burns
Audy Jonathan M.
Brokaw A. Paul
Analog Devices Inc.
Callahan Timothy P.
Luu An T.
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