Jianlong Chen

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Recent progress of wide-band communication systems demands high-frequency circuits. Conventionally, the linearity of the operational transconductance amplifier and capacitor (OTA-C) has been analyzed using Taylor series expansion. Unfortunately, this approach does not predict the frequency-dependent linearity degradation. Thus, to properly design linearized(More)
A 1.5 V low-power stereo audio codec in 0.13 m CMOS is described. The microphone path includes a programmable gain stage with an enhanced transconductance cell followed by a continuous-time ADC with capacitive feed-forward and capacitive direct feedback. The speaker path employs a 1 mA Class-AB speaker amplifier with an improved quiescent current control(More)
Circuit techniques to overcome practical noise, reliability, and EMI limitations are reported. An auxiliary loop with ramping circuits suppresses pop–and–click noise to 1 mV for an amplifier with 4V achievable output voltage. Switching edge rate control enables the system to meet the EN55022 Class–B standard with a 15 dB margin. An enhanced scheme detects(More)
It is shown that a ring R is (von Neumann) regular if and only if every cyclic left R-module is GP -injective if and only if R is left PP and left GP -injective. In addition, two examples are given to answer two open questions in the negative. 2000 Mathematics Subject Classification: 16E50, 16D60