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    74ls 74hc

    hello
    what is the difference between 74ls and 74hc
    i know that the first is schottky and second cmos
    what is the difference and where to use each kind ,and what is the advantage and disadvantge of each familly
    any help? links,pdf,whatever...

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    ass.
    Glaucius Penga



    •   Alt29th June 2003, 14:25

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    difference between 74ls 74hc

    ZeleC:

    The main difference between the LS and HC is the logic of 74XX.

    The 74LS is Transistor to Transistor logic. Uses Shottky transistors to reduce the stored charge and get higher switching speeds then with conventional bipolar transistors.

    The 74HC uses MOSFET technology. Therefore can operate with wider variety of voltages. Power consumption better then TTL (but increases at higher frequencies). Has better noise margins so can work in noisy environments compared to TTL.

    74HC are becoming more and more better replacements to older 74LS

    Transition speeds are not too much different.
    Prop delays for:
    74LS - tpLH and tpHL about 15 nsec.
    74HC - tpd about 18 nsec.

    I don't know if this helps but, I hope this answers some questions.
    WA


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    74ls vs 74hc

    The HC family was intended to exactly duplicate the speed of the LS but with lower power due to being CMOS.



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    74 ac hc difference

    There are a number of other interesting differences. For example, the HC circuits draw very little current at the inputs if you compare it with HC. At the same time, HC (Highspeed CMOS) also preserves other characteristics of the CMOS families, for example you can use 3.0V to power it (and even less, I don't have a datasheet here). Of course, if you to this, the maximum logical levels on the inputs change (with a 3V power suply you won't be able to tie 5V directly to an input, you need at least some minimal level adjustment). This is very interesting for people that design low-speed level shifters (5V-3.3V, seen for example in parallel port to JTAG adapters). Watch it, there is also HCT (Highspeed CMOS, TTL compatible) that makes the power range compatible with the LS series, so you can't power it from 3V. And then there are VHC, LVX, LVC, LVT and others, just to confuse you completely :)



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    74ls projects

    The low power at low freq only. On the high speed, it req approximate as ttl LS series.



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    difference between hc and vhc

    One point that was implied, but maybe not stated. HC has the same functions as the corresponding TTL part, but the parameters are different. i.e. they are not interchangeable in a actual cicuit! The HCT line was introduced to be closer fit and can be interchanged in some cases.



    •   Alt28th August 2003, 16:20

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    74 family 74c 74hc 74ls

    What's the diffirent between 74hc and 74ac (hc and ac)?



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    difference between 74ls and 74hc

    Hope it helps 8) :

    Device Families:

    TTL (74xx) True TTL
    74L Low power
    74S Schottky
    74H High speed
    74LS Low power - Schottky
    74AS Advanced - Schottky
    74ALS Advanced - Low power - Schottky
    74F(AST) Fast - (Advanced - Schottky)
    74C CMOS...................check Vcc levels
    74HC (U) High speed - CMOS (Unbuffered output)
    74HCT High speed - CMOS - TTL inputs
    74AHC Advanced - High speed - CMOS
    74AHCT Advanced - High speed - CMOS - TTL inputs
    74FCT (-A) Fast - CMOS - TTL inputs (speed variations)
    74FCT (-T, -AT) Fast - CMOS - TTL inputs (speed variations)
    74AC Advanced - CMOS
    74ACT Advanced - CMOS - TTL inputs
    74FACT AC, ACT (Q) series
    74ACQ Advanced - CMOS - Quiet outputs
    74ACTQ Advanced - CMOS - TTL inputs - Quiet outputs

    Bus Driver Families

    74ABT Advanced - BiCMOS - Technology
    74ABTE ABT - Enhanced Transceiver Logic
    74ABTH Advanced - BiCMOS - Technology - bus Hold
    74BCT BiCMOS - TTL inputs
    74BTL Backplane - Transceiver - Logic
    74GTL Gunning - Transceiver - Logic
    74GTLP GTL Plus

    Low Voltage Families

    74ALB Advanced - Low Voltage - BiCMOS
    74LV (U) Low - Voltage (Unbuffered output)
    74LVC (R) (U) LV - CMOS (damping Resistor)(Unbuffered output)
    74LVCH Low - Voltage - CMOS - bus Hold
    74ALVC Advanced - Low - Voltage - CMOS
    74LVT (R) (U) LV - TTL (damping Resistor(Unbuffered output)
    74LVTZ Low - Voltage - TTL - High Impedance power-up
    74ALVC (R) ALV - CMOS (bus Hold) (damping Resistor)
    74ALVCH Advanced - Low - Voltage - CMOS - bus Hold
    74LCX LV - CMOS (operates with 3v & 5v supplies)
    74VCX LV - CMOS (operates with 1.8v & 3.6v supplies

    4000 True CMOS (non-TTL levels)

    Zed


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    ttl hc hct ac ls comparison

    If we compare the logic levels;

    LSTTL, compatible with TTL
    HCT, compatible with TTL
    HC, not compatible with TTL



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    difference between cmos 74hc and 74 hct series

    HC - High-speed CMOS
    AC - Advanced CMOS ( higher speeds that HC )
    HCT - High-speed CMOS, TTL compatible (voltage levels compatible with TTL logic levels)
    ACT - Advanced CMOS, TTL compatible (same)

    If you need high speed (check the actual datasheets for numerical values) use ACT. Otherwise you can safely stick to HCT.



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    74ls and 74hc

    Quote Originally Posted by D&S
    What's the diffirent between 74hc and 74ac (hc and ac)?
    gate delay.



    •   Alt4th June 2004, 23:24

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    difference 74ahc 74hc series

    you should to download these datasheet and find difference



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    Re: 74LS & 74hc

    Ive got question.

    Can i use 74AHC to translate voltage level from 3V to 5V ?

    [device 1] - ----3V ----- [74AHC with GND on output_enable_input] ---- 5V? [device2]

    When connected like this im getting 2V output with 3V on input :)
    and its something wrong.

    Do i need AHCT?
    or HCT?

    plz hlp me !



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    Re: 74LS & 74hc

    Ive got question.

    Can i use 74AHC to translate voltage level from 3V to 5V ?

    [device 1] - ----3V ----- [74AHC with GND on output_enable_input] ---- 5V? [device2]

    When connected like this im getting 2V output with 3V on input and its something wrong.
    Why you need this? There are some buffers which will work from 2V supply and are tolerant to 5V inputs, but you want the other way. Why?



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