Posts

VLSI (PROPAGATION DELAY)

Image
 PROPAGATION DELAY: The time required for charging/discharging to change the output from logic 0 to logic 1 or vice versa is called propagation delay. propagation delay(Tpd) should be as low as possible to get fast switching speeds. CMOS is a single RC network and propagation delay of such circuit if excited by V step voltage is :                              tphl = ln(2) Reqn CL = 0.69 Req CL                              tplh = ln(2) Reqp CL = 0. 69 Req CL the total propagation delay is                                tp=(tphl+tplh)/2 = 0. 69(Reqn + Reqp)/2 propagation delay can be reduced in the following ways: Reduced CL : careful design of CMOS reduces diffusion and interconnection capacitances. Increase in W with cons...
Post a Comment
Read more

VLSI (NOISE MARGIN)

Image
 NOISE MARGIN: it is defined as up to what extent noise is allowed so that there is proper extraction of logic 1 and logic 0. NMh is the noise margin for logic high. NMl is the noise margin for logic low. this above noise margin explains that even if you connect the output of the circuit to another circuit at the input that much noise is allowed(NMh, NMl). the gap between Vih and 
Post a Comment
Read more

VLSI (STATIC POWER CONSUMPTION IN CMOS)

Image
 STATIC POWER CONSUMPTION IN CMOS: The current that flows between the power rails when there is no switching activity i.e, there is no switching taking place from 0--->1 or 1---->0 at the input it is more like a steady-state. There is, unfortunately, a leakage current flowing through the reverse-biased diode junctions of the transistors, located between the source or drain and the substrate.  This contribution is, in general, very small and can be ignored. however this leakage current is increased by temperature. Their value increases with increasing junction temperature, and this occurs in an exponential fashion.
Post a Comment
Read more

VLSI (CMOS INVERTER)

Image
 CMOS INVERTER:
Post a Comment
Read more

VLSI (LOGIC STYLE CLASSIFICATION)

Image
 
Post a Comment
Read more

VLSI (MOSFET CAPACITANCES)

Image
 MOSFET CAPACITANCES: speed of the integrated circuit is limited by capacitance so that is why we should study this topic. here we will know the capacitances present in the MOSFET i.e., distributed capacitances( capacitance formed at lower frequency). MOS CAPACITANCES AT DIFFERENT REGIONS:
Post a Comment
Read more

VLSI (STATIC POWER DISSIPATION)

 STATIC POWER DISSIPATION: Assume there is a circuit that consists of a number of MOSFETs. let's take one of the transistors from that circuit, here if Vgs<Vth the transistor is supposed to be OFF. But there is some leakage current that is flowing resulting in a power dissipation. so, when the circuit is in IDLE state or OFF state there is currently flowing through and there is some power dissipation. This Power dissipation which is occurring is called STATIC POWER DISSIPATION.
Post a Comment
Read more