Voltage controlled resistor or low pass
Voltage controlled resistor or low pass
(OP)
Hi
Can any one help I want to make a voltage controlled resistor or a voltage controlled low pass filter.
Many Thanks
Can any one help I want to make a voltage controlled resistor or a voltage controlled low pass filter.
Many Thanks





RE: Voltage controlled resistor or low pass
What sort of resistance or frequencies are we talking and what is the power requirment ?.
And I take it we're talking about a voltage controlled potentiometer and no a Voltage dependent resistor (VDR).
If its the former then there are devices on the market such as DS180X series or DS1869, DS166 or MC3340 to name but a few see the following links for details
http://pdfserv.maxim-ic.com/arpdf/DS1807.pdf
http://pdfserv.maxim-ic.com/arpdf/DS1666-DS1666S.pdf
http://www.mil.ufl.edu/links/datasheets/more.datasheets/mc3340rev6.pdf
I suggest the last link being more suitable.
As for the voltage controlled low pass filter what are you controlling. The upper & lower frequencies, the bandwidth any gain?
Anyhow again there are various devices for configurable filters. The first that comes to mind is the UAF42AP see
http://focus.ti.com/docs/prod/folders/print/uaf42.html
http://www.informatik.hu-berlin.de/~hochmuth/bvp/uaf42.pdf
Any help ?, yes no let me know.
Regards
RE: Voltage controlled resistor or low pass
Thank you for your help so far
Really I need a voltage controlled resistor not digital
the value not that important as long as it can ghange perhaps 10 to 1.
As for the voltage controlled low pass filter the frequency's Im interested in are between 20K to 100K
I have heard that you can use a Cmos 4007 as a voltage controlled resistor is this true and if so how?.
Many thanks
D101
RE: Voltage controlled resistor or low pass
Hope this helps!
RE: Voltage controlled resistor or low pass
Sorry for the confusion!
RE: Voltage controlled resistor or low pass
Just a thought. How about a microcontroller with A/D built in, connected to one of those resistors as mentioned in my previous post. You could also use it to swicth different capacitances and/or resistances in a filter design to affect its Low Pass characteristics.
The controller digitizes the analog voltage and controlls the addressable pots or the capacitor bank
If the above is a bit OTT (Over The Top) then some examples of Melones post are as follows
http://www.national.com/an/AN/AN-32.pdf
(see page 5 on the above link)
http://www.semiconductors.philips.com/acrobat/various/SC07_98_IDEAS_1.pdf
(see page 4 on the above link)
http://physics.bu.edu/py681/lb7_201.pdf
(see page 8 on the above link)
As for the filters then you could try the MAX297 capacitor switched filter however this only goes to 50Khz.
See:-
http://pdfserv.maxim-ic.com/arpdf/MAX293-MAX297.pdf
Any help ?, yes no let me know.
Regards
RE: Voltage controlled resistor or low pass
I've been searching for a light or voltage controlled potentiometer for an art project I'm working on. I contemplated hooking up a CDS cell (Light dependant resistor) to a PIC and then control a digital potentiometer. This seems excessively complicated when I consider the programming of the microcontroller.
Hmm... there must be a more simple solution out there.
Thanks for considering this problem
I found this DC controlled potentiometer circuit. I imagine it would be very difficult to source and there is not a very good data sheet to go along with it.
http://www.nteinc.com/specs/7000to7099/pdf/nte7072.pdf
Rickam.
RE: Voltage controlled resistor or low pass
RE: Voltage controlled resistor or low pass
E. James Angelo, Jr., Electronics: BJTs, FETs, and Microcircuits, McGraw-Hill Book Co., 1969, Sect. 5-4 A Voltage Controlled Diffused Resistor
gives a reasonably good background.