Hey all

So what's your favorite CMOS buffer 5.5V SMT that can source more then 10mA
I am having a hard time finding one greater then 7.8mA on digi
package doesn't matter. Would prefer more then one in a package if possible.

Also looking for the inverting buffer of the same series. No Schmitt

Any recommendations?
I was trying to search for a 74HC but have not had much luck.
Thanks in advance

 

I was looking at this one
Is this considered CMOS? I want to but 5V in and get 5V out which I learned the hard way TTL won't do for me

Data Sheet Here

 

I was looking at this one
Is this considered CMOS? I want to but 5V in and get 5V out which I learned the hard way TTL won't do for me

Data Sheet Here

Yes, MC14000 series parts were some of the earliest CMOS logic parts. (Those parts are not able to drive 10mA.) There are many sources for CMOS logic IC's, but Texas Instruments is very well known; start searching here Logic Devices

 

See

 

What is the current you want to supply ?

I want to but 5V in and get 5V out

Do you need a logic high level out or actually 5V ?


Regards, Dana.

 

Have you looked at the 74HC and 74AC series?
The 74AC08 has at least +/- 24mA drive.

 

74HC is newer high output current Cmos. The maximum allowed output current per inverter or gate is 25mA but the max allowed for a package is only 50mA. The datasheets show the small voltage loss with output current.

A 74HC04 has 6 inverters but many ICs use 2-inputs non-inverting gates with 4 gates per package.

 

So what's your favorite CMOS buffer 5.5V SMT that can source more then 10mA
I am having a hard time finding one greater then 7.8mA on digi
package doesn't matter.

I'd use 74AC125; 4 per package.

 

Another vote for the AC (or ACT) series. Except for the limited operating voltage range, best CMOS ever.

ak

 

I will need 5V out and will need it to be able source 10mA

 

Nothing has an output resistance of zero ohms, even a buffer has some voltage loss when its output is loaded.
The typical output voltage vs output current was shown on older Texas Instruments datasheets graphs.
I cannot look it up because it is on the hard drive of my broken old computer and I cannot find it online.

With a +5.0V supply, the output high is about +4V when it is sourcing 10mA, and its output low is about 1V when it is sinking 10mA. With a 25mA load, its output is about 2.5V.

 

I will need 5V out and will need it to be able source 10mA

Do you expect the outputs to maintain a valid logic level at 10mA sink/source?

74AC125 will sink/source 24mA as follows:


They don't give values for 5V, so pick 4.5V or 5.5V, or interpolate.

 

Hey all

So what's your favorite CMOS buffer 5.5V SMT that can source more then 10mA
I am having a hard time finding one greater then 7.8mA on digi
package doesn't matter. Would prefer more then one in a package if possible.

Also looking for the inverting buffer of the same series. No Schmitt

Any recommendations?
I was trying to search for a 74HC but have not had much luck.
Thanks in advance

As you now know, no logic family has outputs that swing closely rail-to-rail with loads of ~10mA. However, there are discrete MOSFETs and MOSFET pairs that have low Vth suitable for switching fully on with 5V drives and have Ron well below 1Ω (some below 0.1Ω. Such MOSFETs will drive very close to the rails with a load of 0.01A. If you can describe a bit more about what you are trying to do, perhaps other solutions might be suggested. For example, what signal is driving the logic? What actual load is driven by the logic and why are the 10mA/5V goals important?

 

If you really have to have 0V and 5.00V at 0 to 20mA than you will need to have a supply above 5V like 10V and a supply below 0V like -5V. Then use a linear amplifier with feedback not a digital buffer.

 

Thanks for all the replies
Truly helpful

so can someone answer me this
I found this part
74hc series
It says it will source a bunch of output current
It has a 5v supply and yet a v output of 5v typical?
How come there is little voltage loss in this chip?
Thanks

 

One of the things, I think, is they use FETs in place of transistors in the output. A transistor has a higher voltage drop that a FET.

 

Thanks for all the replies
Truly helpful

so can someone answer me this
I found this part
74hc series
It says it will source a bunch of output current
It has a 5v supply and yet a v output of 5v typical?
How come there is little voltage loss in this chip?
Thanks

Mike, you really need to learn to read a datasheet. The 74HCxx series logic devices will drive (considerably) less current than the 74ACxx series already suggested. Look at the section for the symbol "VOH" in the left column. Look at the Conditions column. Find the table cell labeled
"ViN=VIL" and the line in that cell labeled "|IOUT| <5.2mA. Follow that line across to read the values: "6.0V 5.7(V) 5.48(V) 5.34(V) 5.2(V)". There it is shown that with VCC=6V, the worst case "high" output with a load of 5.2mA is 5.2V; i.e. a 0.8V drop from the VCC value. Yes, you could parallel several inverters to get less drop, but you will never get to 0V drop.
There is another group of ICs known as "Gate Drivers" (for driving gates of MOSFET transistors). One device (out of hundreds) that is similar to a simple inverter is the MIC4420 from Microchip Technology. When using a VCC=5V, the output is equivalent to about a 2.5Ω resistor tied to either ground or VCC. Thus, it could drive 100mA from a VCC=5V with only a 0.25V drop from VCC, or 0.025V for 10mA.

@dendad
A FET is a transistor (Field-Effect-Transistor), but it is not a BJT (Bipolar-Junction-Transistor) as used in 74xx logic.

 

74hc series
It says it will source a bunch of output current
It has a 5v supply and yet a v output of 5v typical?
How come there is little voltage loss in this chip?

74HC won't supply "a bunch of current" and maintain a valid logic level.

All CMOS outputs will swing rail to rail as long as they're not loaded. That's why we keep asking you if you need to maintain a valid logic level. If you don't care how much the voltage drops, you can try to source the maximum from the datasheet. If you're also using the output to drive other logic, you shouldn't load it.

 

74HC Cmos logic has up to 10 times the output current of old CD4xxx Cmos when the supply is 3V to 6V.

 

If you don’t actually need the push-pull outputs from a CMOS ‘buffer’ to drive further logic gates, you might want to look into Load Drivers instead.

https://www.digikey.com/product-det...ge/TBD62786AFNGEL/TBD62786AFNGELCT-ND/8569455

Not only can they source plenty of current, they have the added advantage of having their outputs directly across from the inputs, making the layout much simpler.