Thursday, 15 November 2018

CAD LAB EXPERIMENT No. - 2



Aim –    (a) Transient Analysis of NMOS inverter using step input.
              (b) Transient Analysis of NMOS inverter using pulse input.
          (c) DC Analysis (VTC) of NMOS inverter with and without parameters.
Simulator Used – PSpice.
Theory – NMOS functions as an inverter, when operated in only the cutoff and the saturation regions, not in the linear region. When the input voltage is low, NMOS does not conduct, there is no current and a high voltage is received at the output. When the input voltage is increased, NMOS begins to conduct, the voltage drop starts increasing and the output voltage falls. Finally, when the input voltage is high enough to drive the mosfet into saturation, there is a fixed small drop across the mosfet and the output voltage saturates to this low value.
Digital inverter quality is often measured using the voltage transfer curve (VTC), which is a plot of output vs. input voltage. From such a graph, device parameters including noise tolerance, gain, and operating logic levels can be obtained.
Ideally, the 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 the low level. The slope of this transition region is a measure of quality – steep (close to infinity) slopes yield precise switching.
The tolerance to noise can be measured by comparing the minimum input to the maximum output for each region of operation (on / off).

Circuit Diagram –
Result –
Conclusion - (a) Transient Analysis of NMOS inverter using step input has 
                            been performed.
                      (b) Transient Analysis of NMOS inverter using pulse input has 
                            been performed.
                       (c) DC Analysis (VTC) of NMOS inverter with and without
                             parameters has been performed.

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