Dynamic Logic Designs

Dynamic Logic In integrated circuit design, dynamic logic (or sometimes clocked logic) is a design methodology in combinatory logic circuits, particularly those implemented in MOS technology. It is distinguished from the so-called static logic by exploiting temporary storage of information in stray and gate capacitances. Dynamic logic circuits offer several significant advantages over static logic circuits.The operation of all dynamic logic gates depends on temporary storage of charge in parasitic node capacitances, instead of relying on steady-state circuit behavior. Dynamic logic circuits require periodic clock signals in order to control charge refreshing.The capability of temporary storing a state, at a capacitive node allows us to implement very simple sequential circuits with memory functions.  Common clock signals synchronize the operation of various circuit blocks. Power consumption increases with the parasitic capacitances.Therefore dynamic circuit implementation in sm

  Synchronous Dynamic Circuit Techniques: Dynamic Pass Transistor Circuits: -   The circuit consists of cascaded combinational logic which are interconnected through nMOS pass transistors. The operation of the circuit depends on charge storage in theinput capasitor.  and signal timing scheme is also called two-phase clocking. Two-Phase Clock Dynamic Shift Resistor: - A  dynamic shift register  circuit comprises an input terminal and an output terminal. It further comprises a first transfer gate circuit connected to the input terminal for receiving an input signal and transferring the input signal under the control of a first clock signal; an inverter circuit for inverting a level of an output signal of the first transfer gate circuit; a second transfer gate circuit connected to the inverter circuit for receiving an output signal of the inverter circuit and transferring the same under the control of a second clock signal which has a level opposite to that of the first clock signal; a

  Dynamic CMOS Transmission Gate Logic:   Each transmission gate is controlled by the clock signal and its complement. Therefore, the two-phase clocking need four clock signals. As in the nMOS structures, the CMOS dynamic circuit relies on charge storage in parasitic input capacitances during the inactive clock cycles. Dynamic CMOS Transmission Gate Logic-Shift Register:   A dynamic shift register  circuit is provided which comprises an input terminal; an output terminal;  first  transfer gate means connected to the input terminal for  receiving an input signal and transferring the input signal under the control  of a first clock signal.   The basic building block of the shift register consists of a CMOS inverter, which is  driven by a TG.CK=1 Vin is transferred onto the parasitic input capacitance CX. The low on  resistance of TG  results in: 1.      A smaller transfer time compared to nMOS-only switches. 2.      No threshold voltage drop across TG.   Dynamic CMOS Precharge-

  High Performance Dynamic CMOS Circuit: Domino CMOS Logic: Domino  CMOS  logic  circuits which are commonly used in high performance microprocessors for their high speed and area characteristics, are highly sensitive to noise as compared to static gates. Domino logic  is a  CMOS -based evolution of the dynamic logic techniques based on either PMOS or NMOS transistors. It allows a rail-to-rail logic swing. A  buffer , is a basic  logic  gate that passes its input, unchanged, to its output. Its behavior is the opposite of a NOT gate. The main purpose of a  buffer  is to regenerate the input, usually using a strong high and a strong low. A  buffer  has one input and one output; its output always equals its input. Domino Logic Buffer Here we describe CMOS as by given below diagram which consist of cascading of CMOS inverter static stage. During the precharge phase the output node of the dynamic CMOS stage is activated to a high logic level, and the output of the CMOs becomes 0.