Title :
An optimization approach to designing OTAs for low-voltage sigma-delta modulators
Author :
Lampinen, Harri ; Vainio, Olli
Author_Institution :
Digital & Comput. Syst. Lab., Tampere Univ. of Technol., Finland
fDate :
12/1/2001 12:00:00 AM
Abstract :
High performance operational transconductance amplifier (OTA) structures for high-speed, low-voltage, switched-capacitor (SC) based sigma-delta modulator applications have been designed utilizing an efficient circuit optimization strategy presented in this paper. The main idea is to use external programs together with a circuit optimizer to construct flexible optimization algorithms. Optimization goals and constraints are derived from analytical equations and application requirements. Using a 0.35 μm CMOS processing technology a complementary folded cascode feedforward compensated (CFCFC) OTA with 2.5 V supply obtained 470 MHz unity-gain frequency, 350 V/μs slew rate, over 74 dB gain, and over 70° phase margin using 10 pF load capacitances. The optimization strategy was verified by measuring fabricated CFCFC OTA and sigma-delta modulator. The measurement results demonstrate a good agreement with the simulations
Keywords :
CMOS analogue integrated circuits; SPICE; circuit CAD; circuit optimisation; feedforward; high-speed integrated circuits; integrated circuit design; low-power electronics; operational amplifiers; sigma-delta modulation; switched capacitor networks; 10 pF; 2.5 V; 470 MHz; CMOS processing; HSpice; circuit optimization; external programs; flexible optimization algorithms; folded cascode feedforward compensated OTA; high performance OTA; high-speed sigma-delta modulation; low-voltage sigma-delta modulators; result extraction program; switched-capacitor sigma-delta modulator; CMOS technology; Circuit optimization; Constraint optimization; Delta-sigma modulation; Design optimization; Equations; Flexible printed circuits; Operational amplifiers; Switching circuits; Transconductance;
Journal_Title :
Instrumentation and Measurement, IEEE Transactions on
