Operational Amplifiers: Theory and Design TU Delft, the Netherlands, November 6-10, 2017 All Rights Reserved 2017 MEAD Education SA 2017 TU Delft These lecture notes are solely for the use of the registered course Participants and Instructors teaching in the course. No part of these notes may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, photocopying, microfilming, recording or otherwise) without written permission of MEAD Education SA, TU Delft or any of the Authors.
Lesson 3 Output Stages 1
Cell: Output_Stages Output Stages Bipolar Follower Class C CMOS Inverting Amp. Fully Voltagefollower 2
Bipolar Follower Class C Out VCC-VCE SAT Q 1 :off Q 2 :on -V BE V BE Q 1 :on Q 2 :off Input voltage -VEE+VEC SAT Dead Band 3
4
CMOS Inverting Amp. Out M 1 :on M 2 :off VCC M 1 :off M 2 :on Input voltage -VEE 5
Inverting Amplifier Stage Output Current 6
Fully Voltage-follower Out M3 M4 VCC-VDS 1 M 1 :off M 2 :on M 1 :on M 2 :off Input voltage -VEE+VDS 2 7
Class AB Voltage Follower Stage Output Current 8
Output Stages Cell:Output_Stages Assignment 1 Level A Class C output stage DC Sweep analysis. Inverting amplifier output stage DC Sweep analysis. Voltage follower output stage DC Sweep analyses. Conditions: Perform DC sweep analysis from 0 to 2.5 V with a step size of 0.01V. Choose linear sweep. 9
Cell: 07_Output_Stages Assignment 2 Level A Output Stages Analyze the total harmonic distortion at the output using transient analysis & THD function in calculator. Conditions: use a sinusoidal voltage source with a 1.25V CM level Sine signal: amp=1 V, freq=1 KHz, offset=1.25 V; Transient Simulation: Stop Time = 10 m, Accuracy: Conservative After transient analysis, open the Calculator, select the transient voltage waveform (Vt) of the output node, and then choose the thd function under the Special Functions list. Conditions for THD function: From = 0, To = 10m, Number of Samples = 64, Fundamental = 0. The number evaluated by calculator is given as % value. 10
CMOS Inverting Amp. Out M 1 :on M 2 :off VCC M 1 :off M 2 :on Input voltage -VEE 11
Cell Output_AB_FF Feed forward Class AB output stage 12
M2 I 1 xi 4 =I 7 xi 8 =I B4 2 13
M8 M1 M4 M7 I 2 xi 3 =I 5 xi 6 =I B3 2 14
NMOS Only output current 1 (PM) Total Current Total output current Output current of M1 Output current of M2 output current 2 (NM) PMOS Only 15
Cell Output_AB_FB Feedback Class AB with minimum selector 16
M4 M5 17
18
output current 3 (PM) Total output current output current 4 (NM Output current of M1 Output current of M2 19
Output Stages Assignment 3 Level A Sweep IIN from -100u to 100u: 08_Output_AB_FF_Topcell : Plot the current through the output transistors and through the control mesh. 09_Output_AB_FB_Topcell: Plot the current through the output transistors and through the replica transistors 20
Output Stages Assignment 4 Level A Configure the circuit in unity-gain configuration with an input pulse voltage source. Add a resistive load at the output and see the step response of the amplifier. Decrease the load resistor from 10kohm to 10ohm and observe the change in the output current and output voltage Assignment 5 Level B Change the biasing of the output stage and see how it influences the simulation above. Assignment 6 Level C Try to build a complete amplifier with one of the output stages, using feedback network. Refer to Fig. 7.7.2 on pp.255 and 7.7.7 on pp.260. 21