CD4009 application - with one supply voltage? - Page 1
Forum section: electronics / beginners

author: armandine2
author_rank: Frequent Contributor
timestamp: February 22, 2024, 10:19:48 pm
content: I am confused by the CD4009 application shown [as it implies one supply] - but would not be if it was a for CD4049 - am I missing something?

author: Benta
author_rank: Super Contributor
timestamp: February 22, 2024, 10:33:35 pm
content: Nothing to be confused about. V+ connects to both VCC and VDD. The schematic is somewhat simplified.The 4009 could also work as a level shifter, though not very well. The same could be achieved with a resistor divider.It's moot anyway, try to buy a 4009 today.

author: Konkedout
author_rank: Frequent Contributor
timestamp: February 23, 2024, 05:15:08 am
content: I see a bunch of CD4009s here:https://www.digikey.com/en/products/filter/gates-and-inverters/705?s=N4IgTCBcDaIMYBMAsAGFBOEBdAvkAI don't understand the need for a negative supplybythe IC, but the design you show is basically a charge pump voltage inverter. It is "cheap and dirty" and will not perform very well in any sense. You might do well to increase the value of the 0.47 uF capacitor. That old schematic was drawn at a time when ceramic capacitance was bigger and more expensive than it is now.Trying to understand your confusion...notice that the CD4009 is connected to +Vin on its upper left and Ground on its upper right. That counts as running from a single positive supply in my book. Unless you get into something weird stuff like maybe ECL; every small scale integration logic IC I have ever seen runs from a single supply as this one does.

author: wasedadoc
author_rank: Super Contributor
timestamp: February 23, 2024, 10:32:04 am
content: The 7107 is a digital multimeter IC. To be able to measure both positiveand negativevoltages it requires that it has a voltage rail more negative than the COM input jack.

author: wraper
author_rank: Unknown
timestamp: February 23, 2024, 10:49:06 am
content: Quote from: wasedadoc on February 23, 2024, 10:32:04 amAlso although it can work from single voltage if measuring positive voltage only, its accuracy becomes crap close to zero.

author: Zero999
author_rank: Super Contributor
timestamp: February 24, 2024, 03:58:18 pm
content: Why not use a proper charge pump IC?There's the old ICL7660:https://www.renesas.com/us/en/document/dst/icl7660-datasheetThen there are more modern alternatives.NCP7662https://4donline.ihs.com/images/VipMasterIC/IC/ONSM/ONSMS01109/ONSMS01109-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0TCM828/TCM829https://www.farnell.com/datasheets/630371.pdfhttps://www.farnell.com/datasheets/630371.pdf

author: wraper
author_rank: Unknown
timestamp: February 24, 2024, 04:43:18 pm
content: Quote from: Zero999 on February 24, 2024, 03:58:18 pmThe only reason would be cost and availability. ICL7660 is very expensive, NCP7662 has poor availability, TCM828/TCM829 seem to be discontinued. TC7660 has OKish price and availability though.As of CD4009, there are many better choices of CMOS ICs with beefier outputs to use instead of it, 74HC04 for example. You'd probably could get away with a single beefier inverter/buffer in sot 23-5 package.

author: Zero999
author_rank: Super Contributor
timestamp: February 24, 2024, 05:09:43 pm
content: Quote from: wraper on February 24, 2024, 04:43:18 pmYes, generic buffer ICs are typically cheaper and more widely available, but change pump ICs have the advantages of lower ripple, less voltage drop and fewer external components. Take your pick.