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

Thread Starter


Joined Nov 14, 2018
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,



Joined Nov 18, 2016
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.


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