| Electronics > Beginners |
| my analog switch doesn't work as intended |
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| mheruian:
Hello great elders :) I've been self studying analog electronics in a basic level (I'm more of a non-bookish guy so I don't understand deep technical stuffs well but been striving to) and I even complete my setup to enjoy this things ^-^. I have this setup where i generated a sine wave (my analog signal) via 9v transformer (9.5v in actual) wherein I inverse it via op-amp. The inverse and non-inverse sine wave signal is being fed on a SPDT analog switch DG419 (it works fine on this one) so i can switch sine wave signals to be output where in turn be input to SPST analog switch 74HCT4316 but here comes the problem, the analog signal (though distorted) still passes on the SPST analog switch when its off where I guess it shouldn't since I even simulated such setup on a online java applet circuit simulator. Problems i see: 1) SPST analog switch still output the sine wave in a distorted fashion even its off (has even greater amplitude compared to when turned on). 2) The entire circuit is off but still has the sine wave output at the SPST analog switch output. 3) The signal get's noisy when connected to the DG419 and 74HCT4316 analog switches. What I have done: 1) In terms of noise, i had done 2 stages of RC filtering having same values 3.3k resistor and 100nF capacitor which lessens it but decreased the amplitude by 5mV which is I don't wanted to tbh. My circuit: |
| jcw0752:
Have you tried putting a small load on the output of DG419. There is always some small leakage through the solid state switches even when off and there may be some capacitive effects in your circuit too. The high impedance of your scope will not constitute enough of a load to affect the signal that leaks through. John |
| mheruian:
Hi jcw0752, Thanks for the reply :) I really appreciated it. I haven't done that so i guess i would, a simple single resistor would do as a load right? |
| Wimberleytech:
--- Quote from: mheruian on November 12, 2018, 02:29:42 pm ---Hi jcw0752, Thanks for the reply :) I really appreciated it. I haven't done that so i guess i would, a simple single resistor would do as a load right? --- End quote --- I agree with jcw, put a resistor to ground. Try 10K to start. |
| mheruian:
Hi folks, the results are good :D though lastly, i just wanted to ask some tips of ways how can i lower the voltage of the output I had said because it outputs less than 10mV after I had put load resistor. Should it be like this and not around less than 1mV like having 100nV or lower, etc. when turned off?? anyway, i put 100k resistor as a load for the output and it settles out the huge irregular sine wave, previously i started out lower resistance values from 50 ohms but it lessens the value of the sine wave (e.g. 127mV original signal input -> 109mV switched signal output having 50+ ohm). Having 100k or higher resistance stables out the output voltage same on the original input signal. I even tried also doing 3 RC filter stages of the same values but it either goes same or gets worse. I even tried putting some 10uF electrolytic capacitor as a coupling capacitor before the RC filters but still same as the 2x RC filter + Load resistor / no load resistor |
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