A start-up assisted fully differential folded cascode opamp

This paper explains the hidden positive feedback in the two-stage fully differential amplifier through external feedback resistors, and possible DC latch-up during the amplifier start-up. The biasing current selection among the cascode branches have been explained intuitively, With reference to previous literature. To avoid the latch-up problem irrespective of the transistor bias currents a novel, hysteresis based start-up circuit is proposed. An 87dB, 250MHz unity gain bandwidth amplifier has been developed in 65nm CMOS Technology and post-layout simulations demonstrate no start-up failures out of 1000 Monte-Carlo (6-Sigma) simulations. The circuit draws 126uA from a 1.2V supply and occupies the 2184um2 area

Design, Analysis, and Simulation of a Jitter Reduction Circuit (JRC) System at 1GHz

The clock signal is considered as the “heartbeat” of a digital system yet jitter which is a variation on the arrival time of the clock edge, could undermine the overall performance or even cause failures on the system. Deterministic jitter could be reduced during the designing process however random jitter during operation is somehow less-controllable and unavoidable. Being able to remove jitter on the clock would therefore play a vital role in system performance improvement. This thesis implements a 1GHz fully feedforward jitter reduction circuit (JRC) which can be used as an on-chip IP core at clock tree terminals to provide a low jitter clock signal to a local clock network or be used at the clock insertion point to reduce jitter from an off chip signal. It can also be stand-alone and used on PCB designs to reduce jitter on the high-frequency clock signal used on the board. This jitter attenuation circuit is implemented using IBM CMHV7SF 180nm MOSFET process, demonstrates a jitter reduction of at least 8dB at 1GHz with 33ps rms Gaussian random jitter (for a 200ps peak-to-peak randomly changing rising edge input signal)