Hello , I am trying to convert a 3.3V pulse into 5V pulse using 74ABT08 AND gate.
However, when I looked at the datasheet I saw that it reccomended to work in 2.9 out put .
Also its very non reccomended to push it towards 5V output.
Is there some alternative component I could use so It will be producing 5V on the output on the reccomended area?

Thanks.

https://assets.nexperia.com/documents/data-sheet/74ABT08.pdf

 

CMOS

 

Instead of that special purpose gate, use a standard CMOS gate such as the 74HCT08 which has 0.8V Low and 2V high TTL input levels with 5V output.

 

TTL chips have different internal construction - they lack top side switch on the outputs. when it is high, that is thanks to some pullup resistor. even when there IS an output transistor on the high side, it is an NPN coupled with diode and resistor so again... you are NOT getting 5V out even with light load. others consequence of that are obvious, TTL levels are not symmetrical. range for LOW is much smaller than for HIGH (3...4 x). another result is that typical TTL output can sink more current than it can source. the part of the datasheet you are focusing on is when output is high AND it is sourcing MASSIVE current (15mA). obviously pullup resistor will not be able to keep that output at Vcc ... and it does not need to. (it was never designed to do that). it can get closer to Vcc is load is LOW. as others have suggested CMOS logic uses complementary pair of transistors in gate outputs. in other words you have a transistor working as a switch both for LOW and for HIGH state. but... if you are thinking of getting 15mA out of it and still have output levels that approach Vcc and GND, you are gravely mistaken. the output voltage for HIGH and LOW states are only close to GND and Vcc if load and operating frequency are sufficiently low. once you add 50pF as load, you can kiss those nanosecond flanks goodbye.

btw, 74xx08 parts are all same function.
7408 standard logic (TTL)
74LS08 same but with schottky (fast)
74HC08 same but in CMOS (this is the one that gets HIGH output close to Vcc!)
74HCT08 same as above (CMOS) but input logic levels are TLL compatible
and there are MANY more...

 

classic example, note resistor in collector circuit of Q3


another variant, there is a transistor on top side but... it is an NPN... plus there is a diode AND resistor. you would be lucky to get only 1.5V drop across those.

 

Hello cruschow,regarding 74HCT08 can it get input of of 3.3V and still output 5V?
Thanks.

 

No, it's only guaranteed to get to HCT Input voltage levels. You can force it higher though by connecting a resistor from its output to Vcc!

 

Why do you need the output to be 5 V?

How close to 5 V do you need it to be?

How much current does it need to be able to source?

The output levels of logic devices are designed to provide acceptable logic levels to the inputs of other logic devices in the same family (or other specified families). They are not meant to power things or provide specific, regulated voltage levels.

So if you describe what you actually need -- i.e., what the problem is that you are actually trying to solve -- then we can help you find a way to solve it.

 

Hello WBahn , I need to control an RF switch XM-A351-0604D .
this switch is controlled by a biasing network called shown in the link below.
This biasing netwok needs a pulse of 0-5V in the CTL input to switch between states.
I have attached the circuit which I buit which converts 3.3 pulse into 5V pulse.
do you think it will work?
Thanks.

biasing network:
https://catalog.quanticxmw.com/item/bias-and-control/bias-controllers/xm-a9p1-0604d-sp

 

What does the spec document say about what is required? What are the tolerances on the voltage levels? How much current? How fast must the transition be?

 

Hello cruschow,regarding 74HCT08 can it get input of of 3.3V and still output 5V?
Thanks.

View attachment 358348

Yes.
As you can see, the minimum VIH is 2V so 3.3V is more than adequate for an input logic level high.

 

Hello crutshow,I have made the same functionality with different circuit attached.
do you think I will work good in real life as it works in the simulation?

 

It can work, but it is always better to adhere to Keep It Simple design principle.

 

I believe a key point regarding the use of the 74HCT08 hasn't been stated....

It must be powered by 5VDC. When powered by 5 VDC, an input of 2.0V or greater is HIGH, 0.8V or lower is LOW.

 

Hello ,I need to create 4 pulses of 0-5V from 0-3.3V independently with SN74ACT08.
In the simulation it worked great but its in simulation.
In real life as I saw when I trid to biadsfrom TL431 I got 0.6V volts reaching the Vcc.

did I meet the datasheet properly,so it wont burn?
Is there a resistor method to overcome this impedance mismatch ?or something similar?
I know that voltage source needs to deliver voltage if input impedance is low and load impedance is high.
Is there a way to reduce source impedance and to increase load impedance to improve the matching?
Ltspice simulation are attached,
Thanks.