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logic output HIGH from 5V to 12V

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bogdanfirst

New Member
hello!
i got a circuit that outputs logic signals wich have the HIGH of 5V, there are some 74HC CMOS circuits. the problem is that i want the circut to drive some other devices, but those require that i have a 12V output for H and 0V for L.
how could i do that without use of transistors?
could a Schmitt trigger buffer do the job?
if so, wich should i use?
 

bogdanfirst

New Member
well, it is good, but now quite like i need. i checked a datasheet i have and there is somthing i dont understand. it says that for a HIGH leven input voltage for VDD=15V, 11V are needed. so will it work if i apply 5V ? as H ?
 

bogdanfirst

New Member
well, first, i will have to use 2 transistors for each bit, because a transistor inverts the signal.
then, i have 24 bits * 2 = 48 transistors, so they will be a lot more xpensive than using 3 ic's with 8 buffers, or 4 ic's with 6 buffers.
so the circuit will be a lot harder to build, morre expensive, more time consuming, and more space consuming.
 

Roff

Well-Known Member
bogdanfirst said:
well, it is good, but now quite like i need. i checked a datasheet i have and there is somthing i dont understand. it says that for a HIGH leven input voltage for VDD=15V, 11V are needed. so will it work if i apply 5V ? as H ?
I have not used this part, but the way I interpret the datasheet, the input logic threshold is first order dependent on VCC (Vth ~ VCC/2), and only slightly dependent on VDD. See the bottom of the table "Static Electrical Characteristics", and Fig. 9. Neither figure explicitly specifies the behavior with VCC=5v and VDD=12v, but the table "Dynamic Electrical Characteristics" does have timing specs for VCC=5v, VDD=10v and for VCC=5v, VDD=15v, so You should expect it will work for VDD=12v.
 

olly_k

Member
well, first, i will have to use 2 transistors for each bit, because a transistor inverts the signal.
well that depends whether you use an npn or pnp or FET and how you connect it! It is wrong to say it will invert the signal tell us more about the interface etc and we can help!
 

sbayeta

New Member
olly_k said:
well, first, i will have to use 2 transistors for each bit, because a transistor inverts the signal.
well that depends whether you use an npn or pnp or FET and how you connect it! It is wrong to say it will invert the signal tell us more about the interface etc and we can help!
Right, and you didn't say 48 signals
 

bogdanfirst

New Member
Ron, it is exactly as you say that i understand from your datasheet. the problem is the datasheet that i have.....that confuses me.
but still, i have found a circuit in a book that uses this IC just for what i need. so i don't think there will be a problem to use it as i want.
thanks for the help....
yet, are there any other similar IC's. maybe some that don't have the enable pins, and are 2 state, not 3 ? an possibly contain more than 4 shifters?
i'll take a look too.
 
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