Two questions about flip-flops

Discussion in 'General Electronics Chat' started by rampart, Jun 1, 2007.

  1. rampart

    Thread Starter Member

    May 30, 2007
    Please someone help me with the following questions.
    Question#01. Why are flip-flops also referred to by the term "multivibrators"? How can one justify the name "multivibrators" being used for flip-flops?

    Question#02. What is the difference (if any) between a latch and a flip-flop? Is R-S a latch or a flip-flop? By the way, I have seen it being referred to with both the terms. Is that right?

  2. Dave

    Retired Moderator

    Nov 17, 2003
    A multivibrator is an electronic component which implements a two-state system - i.e. the output from the multivibrator has one of two states dependant on the input conditions. There are three broad classes of multivibrator dependant on the stability of the output. Flip-flops are a class of bistable-multivibrators (both outputs are stable) where the output will remain in one or other state indefinately until the input conditions change to the contrary.

    The main difference between latched and flip-flops is that latches are level-triggered whereas flip-flops are edge-trigger. What this means is that in latches the output is responsive to the level of the clock signal, i.e. if the clock is high, the latch is transparent (the input propagates through to the output); whereas in flip-flops the output is responsive to a change in the clock signal, i.e. if the clock signal goes from low to high, at the point of transition of the clock the flip-flop latches over the input to the output - after the change in the clock signal changes in the input with have no effect on the output.

    There are obviously architectural differences at the transistor level for how to implement latches and flip-flops. Typically, (though not exclusively) flip-flops are cascaded latches.