Showing posts from March, 2021

How can a transistor amplify current in a circuit?

My answer   (March 1, 2021)  to SE EE question  How can a transistor amplify current in a circuit? This is one of my favorite topics for discussion that makes me a little extreme in my speech... but I cannot put up with such a simple, clear and obvious phenomenon being explained in vague ways... That is why, when I saw the answers and comments under the question, I wrote my answer in one breath... My answer In fact, OP has understood the naked truth about the transistor "amplifier"... that it is not an amplifier at all... on the contrary, it is an "attenuator". At this stage, OP does not need detailed explanations; he needs confirmation of his guesses. It is considered the transistor is an active element used to build amplifiers... but IMHO this is not true. The transistor is not active but passive element; the only thing that it can do is to dissipate power. So, the transistor is not amplifying but attenuating element. It is just a "resistor" (non-linear,

Differential pair active load contradiction

My answer  (March 1, 2021) to SE EE question  Differential pair active load contradiction And another time I said that Razavi's book is not the place where you can find an intuitive explanation. So even now, seeing the unconvincing explanations for this famous circuit solution... and then the specific detailed explanations in the following answers, I could not stop explaining the idea in ashort answer. There he is... My answer "Active load" is an abstract circuit concept but it can be explained in a simple intuitive way by more elementary electrical concepts as voltage divider, potentiometer, variable resistor, etc... So, M2 and M4 can be considered as two variable "resistors" R2 and R4 in series forming a variable "voltage divider"... or a sensitive "potentiometer" - Fig. 1. It is controlled in a differential manner so that when R2 increases, R4 decreases and vice versa (the resistance crossfades). As a result, the total resistance R2 + R4 s