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Very‐high‐output‐impedance cascode current sources/current mirrors/transresistance stages and their applications
Author(s) -
Zarabadil Seyed R.,
Ismail Mohammed
Publication year - 1992
Publication title -
international journal of circuit theory and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.364
H-Index - 52
eISSN - 1097-007X
pISSN - 0098-9886
DOI - 10.1002/cta.4490200602
Subject(s) - cascode , output impedance , current source , electrical impedance , current mirror , voltage source , electronic engineering , voltage , computer science , input impedance , spice , electrical engineering , transistor , engineering
A reconfigurable MOS/BiMOS cascode current source/transresistance stage with very high output impedance is presented in this paper. A cascode active feedback circuit has been employed to achieve such a high output impedance, which approaches the leakage resistance of a reverse‐biased junction, assuming that the MOS devices have a large channel length and do not exhibit the short‐channel effect. Through small‐signal analysis and SPICE simulation it is shown that the proposed current source/transresistance stage provides an output open‐circuit Thevinin voltage greater than 10 8 V. This is an increase of about four orders of magnitude as compared with the conventional cascode current source with the same output voltage range. For scaled technologies this current source/transresistance stage is shown to be ideal for practical high‐performance analogue circuit design. We have incorporated the current sources with active feedback in the output stage of a folded cascode op amp and obtained a large DC gain improvement without significantly affecting its high‐frequency/transient behaviour.