High dynamic range exponential current generator with MOSFETs
AssigneeKing Fahd University of Petroleum and Minerals
InventorsMunir A. Al-Absi, Karama M. Al-Tamimi
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Abstract
The high dynamic range exponential current generator produces an output waveform (current/voltage) which is an exponential function of the input waveform (current/voltage). The exponential characteristics are obtained in BiCMOS or Bipolar technologies using the intrinsic characteristics (IC/VBE) of the bipolar transistors. The high dynamic range exponential current generator is biased in weak inversion region. MOSFETs biased in weak inversion region are used not to utilize the inherent exponential (IDS/VGS) relationship but to simply implement x2 and x4 terms using translinear loops. The term x4 is realized by two cascaded squaring units. The approximation equation used is ⅇ x ≅ 0.025 + ( 1 + 0.125 x ) 4 0.025 + ( 1 - 0.125 x ) 4 .
Claims4
A high dynamic range exponential current generator with MOSFETs, comprising:
- a numerator current generator;
- first and second numerator current generator squaring circuits connected in-line within the numerator current generator;
- a denominator current generator;
- first and second denominator current generator squaring circuits connected in-line within the denominator current generator;
- a single quadrant divider circuit connected between output of the first numerator current generator squaring circuit and output of the first denominator current generator squaring circuit;
- a bidirectional current mirror circuit connected between output of the second numerator current generator squaring circuit and output of the second denominator current generator squaring circuit;
- numerator current generator and denominator current generator being biased in a weak inversion region that provides an approximation characterized by a relation,
- ⅇ
- x
- ≅
- 0.025
- +
- (
- 1
- +
- 0.125
-
- x
- )
- 4
- 0.025
- +
- (
- 1
- -
- 0.125
-
- x
- )
- 4
- ;
- and
- wherein all components of the exponential current generator are MOSFETs.
Dependencies are inferred from the claim text.