Timestamps: 0:00 Introduction 0:40 Advantage of Differential Signaling 3:33 What is Common-mode input signal? 4:25 Basic MOS Differential Pair 8:41 Differential Amplifier with Common-mode input 13:50 Range of Common-mode input for Differential Amplifier 17:13 Differential Amplifier with Differential Input (Qualitative Analysis)
Thanks for this huge amount of good detailed information about the diff amp. My task is to build a diff amp with two P-channel as a load. How can I make an internal current source with two N-channel and one P-channel?
The polarity of Vo1 and Vo2 is different for only differential input. For the common mode input, it is same. And that's why for the common mode input, the differential output Vo1 - Vo2 is zero.
You need to have a DC Signal (Common Mode Signal) in order for current to flow. The common mode signal essentially turns on both FETs and turns them both on the same degree. Adding small AC input signals on top of that will ensure that there is a differential output at the drains of the transistors.
If true differential input signal is not readily available, then the differential input signal can be applied at only side. And still, it is possible to obtain the similar result. For more info check this simulation. www.multisim.com/content/WfWiSqnoRcTvjcpFrX3KL9/mos-differential-amplifier/ Here, DC voltage on both side acts like a common mode input to both terminals. While, 10 mV input signal is applied at only one input. The Differential gain is 4. So, differential output Vo1 - Vo2 is 40 mV.
Thanks for your good illustration, Could you recommend me good books in this area to study.? And, because I am working in RFIC circuits, do you have any contact information, I can contact you and discuss more about anything that I need to discuss, If you don't mind 😍😍
