What is the different between 74ls series and 74hc series?

74hc series

Any one can tell me what is the different between 74ls series and 74hc series?
THX

74ls vs 74hc

74LS -->TTL serie

74HC -->CMOS serie

and i think the most important diff. is power dissipation.

power dissipation is smaller in 74HC than 74LS

74hc 74ls

THX
but what is the different between TTL and CMOS?
Do they compatible each other? If I want to use 7400 as buffer, which is better?(TTL or CMOS)

74hc vs 74ls

eugenehhk,
"LS" stands for low power Shottky. It is a technology that uses bipolar transistors. The first stage of the gate has the collector "clamped" to the base via a Schottky diode. The diode prevents the first stage from saturating, thus ensuring that the turn-off time of this stage will be minimal.
.
"HC" stands for hign speed CMOS. It uses complementary MOS transistors, along with low value resistors to achieve high speed switching.
.
"HC" is the faster of the two technologies.
.
Compatibility depends on the application. An HC device can adrive a TTL device, but not vice-versa. The reason is that the input switching point of a TTL device is typically around 1.6 Volts. The CMNOS output typically swing s almost rail to rail. However, the guaranteed "1" state output voltage of a TTL device is typically around 2.4 volts (For a 5V supply). The input switching point of a CMOS device is typically around 1/2 the supply voltage (2.5V for a 5 V supplY). As a result, you can not get reliable performance by driving a CMOS input directly from a TTL output. You can partially mitigate this problem by providing a pull-up resistor from the TTL output to the supply.
Regards,
Kral

74hc and 74ls

Hi,
There are many familys in the 74XXX series besides LS and HC.
Like Kral stated the proper type to use depends on what is driving
the input of the gate, and also what the output of the gate is driving.

Bruce

what is the differance between hc and ls in ttl

And there are another families than TTL the mostfastest is the ECL based ina variation of diffamp.

what is a 74hc

THX

speed compatibility between 74ls and 74hc

i thought its actually design techiniques in opamp i think i got to go into deep thanks for a new thought.......i try to get it in few days......

what is different betrween 74ls and 74hc

regarding LS and HC you can get more from datasheet from any vendor with
technical specification, or go through any "logic family" topic in any digital book.

you will get additional info. on more families too.