Hex inverter equivalent not inverter - Page 1
Forum section: electronics / projects

author: JanJansen
author_rank: Frequent Contributor
timestamp: January 30, 2018, 05:42:13 pm
content: Hi i have this hex inverter 7414, i normally use it for MIDI thru,now i am using it to make microcontroller pins have more impedance and bit more voltage,only it is inverted compared to the microcontroller,so my question is :Wha part does the same as this hex inverter, only not inverted, how do you call such part ?thanks

author: Siwastaja
author_rank: Super Contributor
timestamp: January 30, 2018, 05:45:13 pm
content: Buffer.

author: DaJMasta
author_rank: Super Contributor
timestamp: January 30, 2018, 06:06:15 pm
content: Buffer chips like the 7407 exist, but you can also just use a transistor for this (or two as a totem pole, depending on your application). You can also just use two inverters in series.If it's into a micro, though, you can probably just use your inverter and change your code to look for the opposite bit and swap it in software.

author: GreggD
author_rank: Regular Contributor
timestamp: January 30, 2018, 07:00:01 pm
content: I looked for a long time. No good parts found. I use 74ACT04 and double invert or 74ACT573 and set LE=high & OR=low

author: chris_leyson
author_rank: Super Contributor
timestamp: January 30, 2018, 07:37:17 pm
content: Nexperia 74LV17APW, 74AHCT17A, 74AHCV17A, 74HC7014.

author: JanJansen
author_rank: Frequent Contributor
timestamp: February 01, 2018, 04:14:23 pm
content: Thanks for the reply`s all,i looked in the category and also found a 4050, only it is 16 pin not 14, i dont know why they have 2 unused pins.For the 7417 i have to take a look, i want to make the voltage from 5 volt to higher, if i read some datasheets it tells you can go from 12 volt to 5 volt level, that is the other way around.Always takes time to sort out these things, i will get back on this later.I know i can use the ~ code to invert the bits, only if these parts cost the same as a 7414 there is no reason to waste some instruction in this 8 bit chip without compiler optimizing ( XC8 ).

author: Zero999
author_rank: Super Contributor
timestamp: February 01, 2018, 07:03:17 pm
content: Quote from: chris_leyson on January 30, 2018, 07:37:17 pmBear in mind that the 74xx17 has an open collector/drain output stage, so will need pull-up resistors. The 74HC7014 has a full push-pull output stage though.http://www.ti.com/lit/ds/symlink/sn7407.pdfAnother useful schmitt trigger buffer is the 74HC7541.https://assets.nexperia.com/documents/data-sheet/74HC_HCT7541.pdf

author: georges80
author_rank: Frequent Contributor
timestamp: February 01, 2018, 07:54:54 pm
content: Quote from: Hero999 on February 01, 2018, 07:03:17 pm74xx17 is a buffer (not open collector/drain).cheers,george.

author: Zero999
author_rank: Super Contributor
timestamp: February 02, 2018, 10:29:22 am
content: Quote from: georges80 on February 01, 2018, 07:54:54 pmYou're mistaken. The 74xx17 is an open collector buffer. It says so on the data sheet.

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 02, 2018, 10:30:32 am
content: Quote from: DaJMasta on January 30, 2018, 06:06:15 pmPutting two inverters in series seems hacky, until you realise that many chips do exactly that internally.

author: llkiwi2006
author_rank: Regular Contributor
timestamp: February 02, 2018, 10:46:34 am
content: Quote from: Mr. Scram on February 02, 2018, 10:30:32 amIt's because you can only have inverting gates with a cmos process, correct?

author: Zero999
author_rank: Super Contributor
timestamp: February 02, 2018, 10:55:50 am
content: Quote from: llkiwi2006 on February 02, 2018, 10:46:34 amYes. It's the simplest CMOS gate.In practise, it is often better to use a buffer, than two inverters, because most modern CMOS families are buffered, so a NOT gate will actually be three inverters in series, whilst a buffer will only be two inverters in series. Using a buffer, rather than two inverters in series, will quite likely yield a shorter propagation delay.

author: georges80
author_rank: Frequent Contributor
timestamp: February 03, 2018, 12:47:26 am
content: Quote from: Hero999 on February 02, 2018, 10:29:22 amReally?https://assets.nexperia.com/documents/data-sheet/74AHCV17A.pdffor example - where does it say open collector?Or a single gate version that I use oftenhttps://assets.nexperia.com/documents/data-sheet/74LVC1G17.pdfBUFFER... and not open collector/open drain.cheers,george.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 03, 2018, 10:20:24 am
content: Quote from: chris_leyson on January 30, 2018, 07:37:17 pm7014 by the way is "precision" input threshold. Very good for line receiver applications, simple RC timers, delays, that sort of thing.If you need a lot of IO's over a ribbon cable, use a (normal or line-driver output) 74HC output pin -- don't worry about source termination resistor -- and interleave the signals with grounds (this gives about 90 ohms characteristic impedance). The ribbon cable can connect to multiple inputs along its length; at the very end, use a voltage divider type termination resistor, that gives somewhat more than 90 ohms Thevenin resistance, and an open circuit voltage about 0.6 * Vcc. Example would be 180 + 270 ohms (Vth = 0.6Vcc, Rth = 108 ohms). This terminates the line, while reducing the signal voltage a bit (because the line driver has about 30-70 ohms output resistance, depending on type and polarity). Whereas this would be disastrous with regular HC logic, the '7014 has a reliable threshold, giving a modest ~1V noise margin on 5V supplies. (To avoid interference, foil shielding over the ribbon cable may be desirable, as well as ferrite beads.) This goes back to the heady days of computer interfaces, where parallel buses ruled -- the ST-506 HDD interface, for example, uses this design for the control signals (the data, however, is carried on individual, point-to-point cables, with differential (RS-422) signaling, so they weren't quitethatconfident in the method).Downside is the termination resistor consumes 11mA (at 5V) per channel.Tim

author: Zero999
author_rank: Super Contributor
timestamp: February 03, 2018, 05:58:29 pm
content: Quote from: georges80 on February 03, 2018, 12:47:26 amI apologise. I got mixed up with the 74LS17, which is open collector. You're correct, the CMOS versions (74LV17APW, 74AHCT17A, 74AHCV17A etc.) have push-pull outputs.http://www.skot9000.com/ttl/datasheets/17.pdf

author: xygor
author_rank: Regular Contributor
timestamp: February 03, 2018, 06:44:20 pm
content: Bus transceivers can do that. There are all kinds with many features. SN74LVC8T245DGVR is one example that has flexible logic level translation. They are usually more than hex, so not exactly what you asked.