{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

h14_lecture10_2

# h14_lecture10_2 - Lecture 10 Differential Pair Boris...

This preview shows pages 1–5. Sign up to view the full content.

EE 214 Lecture 10 (HO#14) B. Murmann 1 Lecture 10 Differential Pair Boris Murmann Stanford University [email protected] Copyright © 2004 by Boris Murmann EE 214 Lecture 10 (HO#14) B. Murmann 2 Overview Reading 3.5.0, 3.5.3, 3.5.5 (Differential Pair) Introduction The differential pair is the most widely used two-transistor sub-circuit in analog ICs. As we have already seen last time, using a differential pair as a replacement for a simple common source stage eliminates the need for a precise gate bias voltage (V B ). In addition, its differential input and output voltages are more immune to parasitic signal coupling. Today we will analyze some properties of differential pairs and introduce the notion of common- and differential-mode signal components.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
EE 214 Lecture 10 (HO#14) B. Murmann 3 Differential Pair When V ip =V im , and both transistors are identical, we must have I d1 =I d2 =I TAIL /2 How about V ip =V im =1V versus V ip =V im =2V? Makes no difference! From a signal perspective, we care only about the difference of the applied voltages Makes sense to introduce a new variable • V id =(V ip -V im ) I TAIL I d1 V ip I d2 V im EE 214 Lecture 10 (HO#14) B. Murmann 4 Differential and Common Mode (1) We now still need a second variable that describes the potential of nodes V ip and V im with respect to GND Could choose either V ip or V im More elegant solution Cut V id in half and define a new independent variable "Common mode" voltage V ic I TAIL I d1 + V ip - I d2 V id + V im -