Miscellaneous active electrical nonlinear devices – circuits – and – Specific input to output function – Combining of plural signals
Patent
1998-12-15
2000-07-11
Lam, Tuan T.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific input to output function
Combining of plural signals
327356, G06F 744
Patent
active
060878835
ABSTRACT:
Multi-tanh cells constructed in accordance with the present invention provide improved input voltage range by utilizing resistors connected between the emitters of the transistors and the corresponding bias current sources. The resistor values and emitter area ratios are chosen to achieve substantially distortion-free transconductance functions over wide input voltage ranges. This improved input voltage range results in a corresponding improvement in dynamic range because the emitter resistances do not increase the noise significantly at low input voltage levels. In one embodiment, a separate resistor is connected in series with the emitter of each of the four doublet transistors. Another embodiment utilizes only a single bias current source and two emitter resistors to achieve better linearity and lower noise. To achieve higher effective emitter area ratios, an emitter follower scheme can be used to synthesize all or a portion of the area ratio. A series-connected version provides even wider input voltage range.
REFERENCES:
patent: 5532637 (1996-07-01), Khoury et al.
patent: 5936465 (1999-08-01), Kimura
patent: 6037825 (2000-03-01), Kung
Analog Devices Inc.
Lam Tuan T.
Nguyen Linh
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