Question

QUESTION 2: (20 MARKS) +5 V X2 71 QA X2 ×10 5 V Figure Q2.1 The circuit shown in Figure Q2.1, is a multistage amplifier with a differential input stage It uses a folded cascode involving transistor Q3. Note that transistor Q5 operates in class B mode and is off at the quiescent point, while Q4 is ON at the quiescent point with QD sinking its bias current. All transistors have Vad-0.7V, VA-200 V, and β-100 a) Perform a dc bias calucation at the quiescent point ( v 0V, and v, is stabi- lized by external feedback to OV) and determine R so that the reference current IREF is 100μ. For this DC bias calculation you may assume |VBE-0.7V, infinite β , and v. VA -. What are the dc voltages at all the labled nodes (A, B, C, D, E, F, G). b) Provide in tabular form the bias current for all transistors. Provide g and r for the c) Using B 100, find the voltage gain vo/(v-v.) at the quiescent point, and in the d) Find the input and output resistances at the quiescent point ( v, 0V, and vo is signal transistors (Q1, Q2, Q3, Q4, and Q5), and ro for Qc, Qp and QG process verify the polarity of the inputs stabilized by external feedback to 0v) Under what conditions does transistor Q5 turn on? e) Find the input common mode range for linear operation f)

Answer 1