A process and temperature robust constant-gm input/output rail-to-rail op-amp. Issue 6 (June 2015)

• Record Type: Journal Article
• Authors: Shahpari, Nima; Dehghani, Rasul; Rabani, Payam
• Is Part Of: Microelectronics journal. Volume 46:Issue 6(2015)
• Page Start: 506
• Page End: 512
• Publication Date: 2015-06
• Subjects: Microelectronics -- Periodicals; Microélectronique -- Périodiques; Microelectronics; Electronic journals; Journals - contents and abstracts; Periodicals; 621.3805
• DOI: 10.1016/j.mejo.2015.03.015
• Languages: English
• ISSNs: 0959-8324

Abstract

<abstract abstract-type="author" id="ab0005"> <title id="sect0005">Abstract</title> <sec> <p id="sp0090">A rail-to-rail operational amplifier is designed with minimum variation in the input stage transconductance (<inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgj24fgqfcd" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si0041.gif" overflow="scroll" id="d13e935" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>g</mml:mi></mml:mrow><mml:mrow><mml:mi>m</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula>) in standard <inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgj24fgq4pq" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si0042.gif" overflow="scroll" id="d13e944" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>0.18</mml:mn><mml:mspace width=".25em" /><mml:mspace width=".25em" /><mml:mi mathvariant="normal">μ</mml:mi><mml:mi>m</mml:mi></mml:math></alternatives></inline-formula> CMOS technology. In this design, transconductance is maintained approximately constant independent of the operation region of the input transistors (i.e., saturation or weak inversion regions). Unlike conventional methods in rail-to-rail designs in which two complementary differential pairs are used, in this work, by using a single input pair, the sensitivity to mismatches between PMOS and NMOS input transistors is eliminated. A Monte-Carlo simulation with <italic>n</italic>=300 was run to ensure mismatch insensitivity. Simulation results show that the input stage transconductance deviation as the input common-mode voltage varies from rail-to-rail is less than ±<inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgj24fgr5rt" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si0043.gif" overflow="scroll" id="d13e957" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>0.81</mml:mn><mml:mo>%</mml:mo><mml:mo>, </mml:mo></mml:math></alternatives></inline-formula> in typical conditions and at 27 °C. When the temperature varies from −20 °C to 120 °C, the variation does not exceed ±1.28%. Furthermore, the variations of <inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgj24fgr4x2" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si0044.gif" overflow="scroll" id="d13e972" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>g</mml:mi></mml:mrow><mml:mrow><mml:mi>m</mml:mi></mml:mrow></mml:msub></mml:math></alternatives></inline-formula> in two long-channel (<italic>L</italic>=1 µm) and short-channel (<italic>L</italic>=0.18 µm) cases are ±0.85% and ±0.9%, respectively. This proves that the introduced circuit works properly regardless of the channel length of the input pair.</p> </sec> </abstract>