A t flip flop needs a clock signal to operate correctly.

That clock signal will be provided by a LC tank circuit.

Can I just connect the CLK pin to one of the nodes of the LC circuit or is it more complicated than that?

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Do I need to ground the LC circuit?

  • \$\begingroup\$ "A T flip-flop needs a clock signal to operate correctly." Where did you get that idea? What did you think was going to get the oscillation going? How will that generate the right logic voltages for the CLK input? \$\endgroup\$
    – Transistor
    Oct 8, 2020 at 21:50
  • \$\begingroup\$ My bad. Most of the projects of a t flip flop I have found are digital counters that is why I posted that. I knew the oscillation was going to die off. \$\endgroup\$
    – Se1fie
    Oct 8, 2020 at 21:56
  • \$\begingroup\$ That's fine. I just wanted to prod you into thinking. Notice that you have only one connection between the tank and the rest of the circuit so it couldn't do anything anyway. See Chris' answer for ideas. \$\endgroup\$
    – Transistor
    Oct 8, 2020 at 22:01
  • \$\begingroup\$ Newbie type question. expert answer ... tinyurl.com/y2rn9pqo showing internal ESD protection diodes with an XOR gate to enable LRC clock with random output when stopped, like rolling the dice 0 or 1 \$\endgroup\$ Oct 8, 2020 at 23:04

1 Answer 1


No, you need an actual oscillator circuit to be governed by the LC tank.

You can look up various ways to make those with a transistor, (ab)using various logic gates, etc.

In practical terms though, this is not really the best way to generate a clock for a flip flop, which additionally needs to be square-ish and transition between good logic levels. Better options could include:

  • A small "clock oscillator" module sold just for this purpose and dirt cheap. Get one for at most a few MHz.

  • A 555 (especially a CMOS version) with an RC timing circuit, handy if you want to watch with slower test equipement

  • a dedicated clock output, timer output or rapidly twiddled GPIO from an MCU eval board you might have on hand (eg an Arduino), advantageous again as you can run it slowly to more easily see what happens

  • a debounced pushbutton - letting you literally run things at human speed. Passing a button through MCU code could be any easy way to improvise this, too.

Somewhat implicit in this (at least apart from the first option of a clock oscillator module) is the likelihood that in working with a loose flip-flop, you are working on an formal or self educational project, rather than trying to build an actual personal-use or commercial product, as such today would typically use much higher level integration than a bare flip-flop, or be implemented largely in MCU software.


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