4069 as variable resistor

[prprog]

I try to search the web on this (read about it a long time ago)->used a 4069 hex inverter as a variable resistor. Any idea on how this can be done?

Thanks

 

[Hero999]

I don't see how it can be done, it's a buffer not a variable resistor.

 

[kchriste]

I've seem them used as a VCO and an analog amplifier, but never as a resistor. What are you trying to build?

 

[audioguru]

A long time ago the CD4007 was shown how it could be used as a variable resistor.

 

[Sceadwian]

Switched capacitor filter?

 

[Hero999]

A long time ago the CD4007 was shown how it could be used as a variable resistor.

Let me guess, I assuem it involved operating the MOSFETs in the ohmic region.

 

[audioguru]

Let me guess, I assuem it involved operating the MOSFETs in the ohmic region.

Yes, and they have two very well matched Mosfets because it is monolithic, either N-channel or P-channel.

 

[kchriste]

The neat thing about the CD4007 is that you have semi independent access to the individual MosFets in the IC and can operate both the P and N channel devices as open drain. Maybe prprog should use this IC or a discreet MosFet for his "voltage controlled resistor".

 

[Boncuk]

He could also use a 4066 analog switch and has 4 bits to change resistor values.

Hans

 

[Mikebits]

Analog Devices: AD5228: 32-Position Manual Up/Down Control Potentiometer :: Digital Potentiometers :: Digital to Analog Converters