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6.376 Fall ‘03 Final Project -- Resonant Filter with Improved Offset Correction. Armando Mesa & Ken Taylor. g mOC /g m3. 1/( t lpf-old s + 1). v 1. v 1. v in. v in. v out. v out. g m1 /g m3. g m1 /g m3. 1/( t 3 s – 1). 1/( t 3 s – 1). 1/( t 2 s + 1). 1/( t 2 s + 1). +. +. +. +.
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6.376 Fall ‘03 Final Project -- Resonant Filter with Improved Offset Correction Armando Mesa & Ken Taylor
gmOC/gm3 1/(tlpf-olds + 1) v1 v1 vin vin vout vout gm1/gm3 gm1/gm3 1/(t3s – 1) 1/(t3s – 1) 1/(t2s + 1) 1/(t2s + 1) + + + + -AgmOC/gm3 1/(tlpfs + 1) Original Offset Correction: tlpf-old = Clpf / gmlpf DC Gain = gm1/(gmOC + gm1) For 50dB attenuation, need gmOC > 317.2 gm1 Way too much power required to do this! Improved Offset Correction: tlpf = Clpf(1 + A) / gmlpf DC Gain = gm1/(AgmOC + gm1) High-gain voltage stage A allows lower power Can also use miller effect across A to slow down LPF – smaller cap needed
Frequency Response @ Q = 2, f90 = 10kHz • < 1dB Variation from unity -- 70 Hz to 3kHz • HF Attenuation > 51dB (>50dB) • Attenuation at 0.1Hz = 51.5dB (>50dB) • LF Rolloff = 40 Hz (<50Hz)
Stability -- Stepping Vref • Peak Overshoot = 100% (not good… wanted < 10%!) • Settling to 5% in 30ms (< 50ms … exceeds spec by over 20%)
DC Behavior • Flat for 300mV (>100mV … exceeds spec by over 20%)
Transient and Linear Range Time (ms) • Power-on time < 1ms • Noise = 320mV, Vmds = 160mV @ Q = 2 • @f90, Vinmax > 0.64Vpp, DR > 72dB (>60dB, exceeds spec > 20%)
Area < ¼ of Chip • Total Power = 20mW (< 30mW … exceeds spec by > 20%) • Uses Common Centroid for all diff pairs, current mirrors, and cascode pairs.