Electronics > Beginners

HEF4013 flip flop question

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Zero999:
I can't see anyone recommending TTL for anything nowadays. You could go with LS, but raw TTL is obsolete and many parts are unobtainable or expensive.

There's the 74LS74 or the HCMOS equivalents 74HC(T)74, but they're not pin compatible with the 4013.
https://assets.nexperia.com/documents/data-sheet/74HC_HCT74.pdf
https://assets.nexperia.com/documents/data-sheet/HEF4013B.pdf

David Hess:

--- Quote from: Chris Wilson on May 22, 2019, 11:52:31 am ---Do you think I should stick with the HEF4013 as it appears to breadboard fine, or go to a faster TTL IC?
--- End quote ---

I suspect it would be easier to just add a level shifter using a single bipolar transistor.


--- Quote ---I don't suppose there's a pin compatible TTL flip flop I could just substitute and observe the results, is there....? Having a variable voltage supply for the 4013 means I can supply 5V instead for a TTL IC.
--- End quote ---

I am not aware of a TTL direct replacement for the 4013.  The common 7474 uses a completely different pinout.

T3sl4co1l:
If this is directly the circuit you've been playing with over the years, it's because the drive is AC coupled like it's an RF amplifier, but it's not, it's going from logic to logic.  It makes no damn sense, and should simply be connected straight through (with a comparator if necessary, to boost it to proper logic level).

Tim

Chris Wilson:

--- Quote from: T3sl4co1l on May 23, 2019, 04:24:29 am ---If this is directly the circuit you've been playing with over the years, it's because the drive is AC coupled like it's an RF amplifier, but it's not, it's going from logic to logic.  It makes no damn sense, and should simply be connected straight through (with a comparator if necessary, to boost it to proper logic level).

Tim

--- End quote ---

Hi Tim, thanks for the reply. it is and it isn't the same :) It's an MF version of the LF one that works fine, but the FET driver didn't like the higher frequency and gets damned hot. So I converted to an  HEF4013 to halve and give a Q / Not Q out to two separate, higher speed, high power FET driver IC's. The exciter uses a Si5351A which uses its  CLK0 pin output direct to provide the X2 input capacitively coupled with a 220 nF poly cap to the HEF4013. That in turn outputs to the FET driver its inverted and none inverted signals at the desired frequency (around 475.750 kHz) via another 220nF cap on each output direct to the FET drivers input pins. If I do not capacitively couple to the FET driver IC's it will put one FET into permanent conduction with no input signal so I am afraid i don't understand when you say it should be connected straight through. All similar amps do this or use transformer coupling. Sorry to be dense, it's the way I am.... ;) The exciter is this circuit withot the three BS170's, as I say, just using the output from CLK0 via 220nF to the HEF4013 input. Attached is the scope pattern from CLKO

Thanks again

T3sl4co1l:
Yeah, bingo.  Si5351 is a 3.3V device.  You need a logic level converter from 3.3V to 12V.

Tim

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