1. Sampling

2. Introduction  Sampling refers to the process of converting a continuous, analog signal to discrete digital numbers.

3. Sampling

4. Cont.,  When an analog voltage is directly connected to the input of an ADC, the conversion process can be affected if the analog voltage is changing during the conversion time.

5. Sample and Hold circuit  The stability of the conversion process can be improved by using a sample and hold circuit.  It is used to sample an analog input voltage for a very short period of time and to hold the analog voltage constant while the conversion takes place.

6. Sampling and Hold circuit

7. Sample and Hold circuit waveform

8.  The waveform refers to the case of positive going S/H pulses.  This circuit track the input signal when the command is high and holds the input signal when the command is low.

9. Ratio estimation of sampling survey animation

10. Sampling rate  The sampling rate is the number of samples of data taken in one second for each channel of audio being recorded.  CDs are recorded at 44,100 samples per second.

11. 1000hz signal recorded at 8000 samples per second sample rate

12. 1000hz signal recorded at 44,100 samples per second

13. Oversampling  Oversampling is the mathematical interpolation of data.  It allows a signal with x number of samples/s to be increased to any multiple of x. A 44k rate signal with 2 times oversampling will have 88,000 data points from which to decode the recorded audio.

14. Oversampling

15. Sample and hold amplifier  The Op-amps A1 and A2 are worked as voltage followers.  The output of A1 is connected to the input of op-amp A2 through a switch.

16. Working of Sample and hold amplifier  The switch is controlled by a logic signal, meaning that a high input ‘closes’ the switch and a low input ‘opens’ it.  When the switch is closed, the capacitor rapidly charges to V in.

17. Sample and Hold Amplifier

18. Cont.,  Now the output of second Op-amp V out is equal to V in.  When the switch opens, the capacitor retains its charge.  Ideally, the output holds at a value of V in.

19. Cont.,  If the switch is suddenly opened, the capacitor voltage represents a sample of the input voltage at the switch was opened.  The capacitor then holds this sample until the switch is again closed and a new sample taken.

20. The End …… Thank You ……