N-bit sampling AdC has an rms quantization noise of q/(sgrt 12)uniformly distributed within the Nyquist band of dC to fs/2(where q is the value of an lsB and fs is the sampling rate). Therefore, its SNR with a full-scale sinewave input will be(6.02N+ 1.76)dB. If the adC is less than perfect, and its noise is greater than its theoretical minimum quantization noise then its effective resolution will be less than N-bits. Its actual resolution(often known as its Effective Number of bits or ENOB)will be defined by ENOB= SNR-176dB 6.02dB SAMPLING ADC QUANTIZATION NOISE OUTPUT SIGNAL ADC RMS QUANTIZATION NOISE =gN 12 Figure 3.6 If we choose a much higher sampling rate the quantization noise is distributed over a wider bandwidth as shown in Figure 3.7. If we then apply a digital low pass filter LPF) to the output, we remove much of the quantization noise but do not affect the wanted signal- so the ENOB is improved. We have accomplished a high resolution A/d conversion with a low resolution ADC6 N-bit sampling ADC has an rms quantization noise of q/(sqrt 12) uniformly distributed within the Nyquist band of DC to fs /2 (where q is the value of an LSB and fs is the sampling rate). Therefore, its SNR with a full-scale sinewave input will be (6.02N + 1.76) dB. If the ADC is less than perfect, and its noise is greater than its theoretical minimum quantization noise, then its effective resolution will be less than N -bits. Its ac tu al r eso lutio n ( o fte nk n o wnas its E f fe c tiv eNu m bero f B its or E N OB )will bede f ine d by ENOB SNR dB dB = - 176 6 02 . . . SAMPLING ADC QUANTIZATION NOISE Figure 3.6 If we choose a much higher sampling rate, the quantization noise is distributed over a wider bandwidth as shown in Figure 3.7. If we then apply a digital low pass filter (LPF) to the output, we remove much of the quantization noise, but do not affect the wanted signal - so the ENOB is improved. We have accomplished a high resolution A/D conversion with a low resolution ADC