CMOS SR flip-flops

171

01:46:35

These are exceedingly low-current once they've been put into a steady state, but they use more transistors than other discrete-component flip-flops.

Top: simple momentary switch control.

Bottom: logic inputs.  Note one input is negative logic.

(Oops! I forgot a connection in the bottom one.  It was relying on stored charge.  Fixed now.)

published 7 years ago

jason9

7 years ago

Nice.

hurz

7 years ago

the Top one needs a resistor to not be short circuit by set reset switch http://everycircuit.com/circuit/6417067854266368

lenzrulz

7 years ago

Very nice, thanks for publishing...👍

eekee

7 years ago

@hurz: the transistors switch so fast the current flow can't cause any harmful heating. Compare normal CMOS, where such a "short-circuit" exists every time a gate switches, but it takes upwards of hundreds of millions of transistors switching at frequencies over 300MHz to build up any serious heat. In simulation here, even at 10ns/s, the simulator only registers a little over 100mA for what must be less than a picosecond, dropping immediately to about 25mA for about 4ns, then reducing down to perhaps 1mA in 40ns.

hurz

7 years ago

i agree, shot trought is not an issue. Only in big integrated circuits it starts to be a heating problem. But what i was talking about is, your topology are two inverter in series, while the output of one is connected to an input of the other. In between in- and out- you connect the switches which short circuit the inverter output to rail voltage! A resistor avoids this short.

eekee

7 years ago

If oeak current is micro-amps, why does it matter? :)

hurz

7 years ago

100million gates switching at the same time will be a problem. But we are talking about two different things. One is the shoot through current and the more important thing for your circuit is driving output against output!

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