A very high output impedance tail current source for low voltage applications

Citation
E. Ibaragi et al., A very high output impedance tail current source for low voltage applications, IEICE T FUN, E83A(2), 2000, pp. 204-209
Citations number
10
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Eletrical & Eletronics Engineeing
Journal title
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES
ISSN journal
0916-8508 → ACNP
Volume
E83A
Issue
2
Year of publication
2000
Pages
204 - 209
Database
ISI
SICI code
0916-8508(200002)E83A:2<204:AVHOIT>2.0.ZU;2-7
Abstract
A tail current sourer is often employed for many analog building blocks. It can limit the increase uf excess power. Il can also improve CMRR and PSRR. In this paper, we propose a very high output impedance tail current source for low voltage applications. The proposed tail current source has almost the same output impedance as the conventional cascode type tail current sou rce in theory. Simulation results show that the output impedance of the pro posed circuit becomes 1.28 G Omega at low frequencies. Applying the propose d circuit to a differential amplifier. the CMRR is enhanced by 66.7 dB, com pared to the conventional differential amplifier. Moreover, the proposed ci rcuit has the other excellent merit. The output stage of the proposed tail current source can operate at V-DS(sat) and a quarter of V-DS(sat) of the s imple current source in theory and simulation. resprctively. For example. i n the simulation, when the reference current I-REF is set to 100 mu A. the minimum voltage of the simple current source approximates 0.4 V. whereas th at of the proposed current source approximates 0.1 V. Thus, the dynamics ra nge can be enlarged by 0.3 V in this case. The value is still enough large value for low voltage applications. Hence, the proposed tail current source is suitable for low voltage applications.