Thursday, 15 November 2018

CAD LAB EXPERIMENT No. - 3



Aim –    (a) Analysis of CMOS inverter using step input.
              (b) Transient Analysis of CMOS inverter using step input with
                   parameters.
              (c) Transient Analysis of CMOS inverter using pulse input.
              (d) Transient Analysis of CMOS inverter using pulse input with
                    parameters.
              (e) DC Analysis (VTC) of CMOS inverter with and without 
                   parameters.
Simulator Used – PSpice.

TheoryCMOS is also sometimes referred to as complementary-symmetry metal–oxide–semiconductor. CMOS uses complementary and symmetrical pairs of p-type and n-type metal oxide semiconductor field effect transistors (MOSFETs) for logic functions.
When input is HIGH, the gate of PMOS is at 0V relative to its source i.e. VGS1 =0V. Thus, PMOS is OFF. On the other hand, the gate of NMOS is at + VDD relative to its source i.e. VGS2 = + VDD. Thus, NMOS is ON. This will produce Vout ≈ 0 V.
When input is LOW, the gate of PMOS is at a negative potential relative to its source while NMOS  has VGS = 0 V. Thus, PMOS is ON and NMOS is OFF. This produces output voltage approximately + VDD.
Digital inverter quality is often measured using the Voltage Transfer Curve (VTC), which is a plot of input vs. output voltage. Ideally, the voltage transfer curve (VTC) appears as an inverted step-function - this would indicate precise switching between on and off - but in real devices, a gradual transition region exists. The VTC indicates that for low input voltage, the circuit outputs high voltage; for high input, the output tapers off towards 0 volts. The slope of this transition region is a measure of quality - steep (close to -Infinity) slopes yield precise switching.

Circuit Diagram –
Result –
Conclusion - (a) Analysis of CMOS inverter using step input.
                       (b) Transient Analysis of CMOS inverter using step input with
                            parameters.
                       (c) Transient Analysis of CMOS inverter using pulse input .
                       (d) Transient Analysis of CMOS inverter using pulse input with
                              parameters.
                       (e) DC Analysis (VTC) of CMOS inverter with and without
                              parameters.

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