ECE Projects
 
 

 

Electronic Projects

       AudioRF Circuits 
     
      Event Detection Circuits 
         
      Math Function Circuits 
         
      Measurement Circuits 
    
      Motor Control Circuits 
         
      Power Supply Circuits 
         
      Sensing Circuits 
         
      Special Function Circuits 
         
      Switching Circuits 
     
      Timing Circuits 
         
      ToneWave Generators 

Digital Counter Circuits

Figure 1.  Circuit Diagram for a 'Ripple' or Asynchronous Counter

The circuit in Figure 1 is that of a 4-bit asynchronous counter, also known as a 'ripple counter'. It consists of 4 J-K flip-flops whose J and K inputs are tied to logic '1'.  This connection causes the output of each J-K flip-flop to toggle every time it gets a clock pulse. By using the output of the previous flip-flop to clock the next flip-flop, a 'rippling' effect is achieved causing the flip-flops to count in binary fashion.

 

Figure 2.  Circuit Diagram for a Synchronous Counter

The circuit in Figure 2 is that of a 4-bit synchronous counter. It consists of 4 J-K flip-flops, all of which are clocked at the same time, hence the name 'synchronous counter'.  Thus, the toggling of the output of the flip-flops in this counter depends on the states of their J and K inputs. Recall that the J-K flip-flop's output will only toggle when both J and K are 'high'.

The first flip-flop (lease-significant bit) of a synchronous counter has its J and K inputs directly tied to logic '1'.  This causes its output to toggle automatically every time it gets a clock pulse. The second flip-flop's J and K inputs are directly tied to the output of the first flip-flop.  Thus, even if they get clocked at the same time, the second flip-flop will only toggle half the times as the first one. The subsequent flip-flops' J and K inputs are tied to an AND gate whose inputs are tied to the outputs of the last two flip-flops before it. This ensures that each of these flip-flops will toggle at half the rate as the flip-flop before it, even if they are all clocked at the same time.