Dual D-Type Flip Flops of 74ALS74 and 74LS74

Thread Starter

kelumsd

Joined Nov 14, 2018
14
Hi all,

I'm trying to complete an electronic project (PLL FM transmitter) which consist Dual D-Type Flip Flop of 74ALS74. Unfortunately I couldn't find that IC within my area.

But later I have found logically identical 74LS74 Dual D-Type Flip Flop. But I not sure I can use 74LS74 instead of 74ALS74. Both IC datasheets are mostly identical in logical an pin layout wise.

So I would like to know kindly anyone can explain any possibility that I can use 74LS74 instead of 74ALS74.

I have attached the circuit diagram, the IC1 is the 74ALS74.
Please kindly assist me.
Also datasheets of both 74ALS74 and 74LS74 are attached.

Best regards,
Kelum.
 

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dl324

Joined Mar 30, 2015
8,877
Welcome to AAC!

74ALS is twice as fast as 74LS. What is the maximum clock frequency to the flip flops?
 

crutschow

Joined Mar 14, 2008
23,314
It's likely they used the ALS version because the LS version is not fast enough.
Can you find the S version?
 

Thread Starter

kelumsd

Joined Nov 14, 2018
14
It's likely they used the ALS version because the LS version is not fast enough.
Can you find the S version?
Hi, thanks for reply :)

You mean, Can I find 74S74? Yes, hopefully I think I can find 74S74....
 

ArakelTheDragon

Joined Nov 18, 2016
1,265
The hardware implementation inside is different. Like said in the upper posts they have different speed because:
74LSxxx series is low-power Schottky and the 74HSxxx series is high-speed CMOS and so on.
 

ebp

Joined Feb 8, 2018
2,332
The SN74ACT74 may be usable as an alternative. Note that it must be the T version to have TTL-compatible input characteristics.
 
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