digital switch

[smitchell82]

Hi,

Im wondering if anybody knows of a simple digital switch that will connect 2 pins on a low input and put a huge resistance between the two on a high input (just a normal digital switch).

or is there a circuit that can do the same thing?

Its for an oscillator circuit operating at up to 1kHz so if a circuit is suggested, it probably should be relatively fast. thanks a lot.

Sam

 

[Exo]

a 4016 or 4066 will do that...
It contains 4 switches in one package. It switches on when the control is high. But just invert your signal to make it work...

Ron of these devices is somewhere around 100ohm. Check to see this isn't a problem first

datasheet:
https://www.electro-tech-online.com/custompdfs/2003/09/74HC_HCT4016_CNV_2.pdf

 

[smitchell82]

Hi, the on resistance of the switch seems to be a huge problem. the circuit i am looking at making is for a voltage controlled oscillator, where a capacitor is connected to ground once the switch is closed and discharges. with a 100ohm resistance, the capacitor doesn't discharge.

any other idea's?

 

[Exo]

You could use an N-channel FET as a switch, there are fet's out there with an Ron of only few milliohms. Problem with these is that when turned off; they have quite a large capacitiy (approx 1 or more nF) between drain and source wich might also be a problem (cause small signals will still get trough due to the capacitance)

only thing besides that would be a QS3384 bus switch (10 switches)
Ron is 4 to 5 ohm and capacitance is very small. But they're only available in small SMD packages and not so cheap (over here anyway).

https://www.idt.com/docs/QS3384_DS_27540.pdf