Experiment #02Experiment #02I replaced the CV generation section (SW2, R3, R4 and C3) and used instead a potentiometer to provide a manually-controled CV. The pot was used as a voltage divider and it's value was 500k lineal. Then I manually sweeped the pot.
The 4016 responded switching on/off as expected, without any pops or noises. On the extremes of the pot (the 0v and 9v lugs) and for the most of the pot rotation the switch made no action. That is, it stayed ON with high voltages and OFF with low voltages. Then there's this little transition area, around the middle of the rotation (and around the middle supply voltage) where the signal slowly comes ON (or OFF), but making no sudden changes or pops.
When I repeated the same test on the 4066, that little transition area dissapeared. When the voltage crossed the middle point, the switch changes state suddenly and with an anoying noise. I noted also the change was more abrupt when switching off.
Interesting, so I moved on to the next experiment.
Next, decided to take some measures, I repeated Experiment #02-a but instead of switching audio, I used the 4016 to switch a Led. This is the setup:
I started sweeping again on the pot, founding similar results as before, but this time getting a visual cue of the situation. Then I measured some currents and voltages and plotted the next graph:
In the particular chip I used, the transition area is a little zone between
4.47v and 6.45v (using a 9v supply), though most action takes place from
4.69v
to 4.9v. Below 4.47v, the switch is open; above 6.45v, the switch is closed.
So this little experiment leds to think this IC can be used as a voltage-controled variable resistor, but the biasing would be kinda critical, as the usable zone is like 200mv wide. It may even be used as an amplifier! Things to test later.
Miguel Canel, Buenos Aires, Argentina
bioroids.miguelNOSPAM@yahoo.com.ar (Quitar NOSPAM) http://www.bioroids.com.ar