Advanced Electronics: Transistors Modelling and Amplifiers - EE3049

This document presents solutions for an advanced electronics assignment focusing on transistor modeling, current mirrors, and amplifier design. The assignment covers the analysis of different transistor types (NPN, PNP, NMOS, PMOS) and their input characteristics. It includes the design and analysis of current mirrors using NMOS and PMOS transistors, along with their advantages, disadvantages, and methods to improve performance. The solution also involves the biasing of BJT and MOS transistors and the simulation of amplifier circuits using SPICE, with the results showing parameters like input impedance, output impedance, voltage gain, and transconductance. The document provides detailed explanations, circuit diagrams, and simulation results to aid in understanding and completing the assignment effectively.

Electronics engineering
Assignment 1 - Advanced Electronics - Transistors Modelling
Part 1
Solution 1:
NPN ( Input Char)
Pnp
nMos

pMOS
Solution 2:
Analysis:
The characteristics obtained show that in case of npn transistor the current stats to rise after a
certain voltage is reached. This voltage is Vbe at which the transistor becomes ON.
In nMOS, the threshold voltage is positive and in pMOS the threshold voltage is negative. In
NMOS, the current rises in the positive direction but in pMOS it rises in the negative
direction.
In DnMOS, the conduction begins from the beginning itself as the channel is already present
and no threshold voltage needs to be overcome.
Part 2
Task 1
Solution 1:
 Basic current mirror using nmos

 Using pmos
 Wilson CM

 Using pmos

Solution 2:
Advantages:
Current mirror can be used to design a constant current source.
Disadvantages:
But noise may be added to the circuit due to the presence of a current mirror. If no resistance
is present at emitter, then noise may be more. Another disadvantage is that distortion may be
added by the current mirrors. Distortion will be high if the value of Vbe is different for both
the transistors and emitter resistance is present.
Solution 3:
Solutions -
The noise can be decreased by using large value resistance at the emitter. The solution for
distortion is the use of 2 transistors which are matched. Also, the resistance connected at
emitter must be more than dynamic impedance of the transistor at emitter.
Solution 4:
 Improved Wilson CM

 Using pmos
 Cascade CM

 Using pmos

These circuits show better response compared to normal current mirror.
Task 2
Solution :

Assignment 2 - Advanced Electronics - Transistor Amplifiers
Tasks
Solution 1 , 2 :
Methods for biasing BJT and MOS transistors:
Biasing of BJT is done to stabilize Ic and Vce so that the transistor remains in active region
for entire range of the input signal.