MILLER THEOREM || ECT202 ANALOG CIRCUITS || KTU || MODULE 2

Hi all, today we are discussing about Miller's theorem. So it is an important theorem usually used to analyze transistor at high frequencies. We are going to learn about transistor high frequency analysis in this video. When a transistor is analyzed at high frequencies, there will be an effect of a feedback capacitor. Miller's theorem is used to analyze that effect. Miller's theorem is a theorem used to analyze a transistor at high frequencies. In Miller's theorem, it discusses the effect of this feedback component on input side and output side. You can see the feedback component Zf here. Miller's theorem discusses the effect of Zf on input side and output side. Miller's theorem discusses the effect of feedback component on input and output side of the amplifier. The input current I1 is completely flow through the feedback component. The input current I1 is completely flow through the feedback component Zf. The input resistance of an amplifier is a very large value. The input current I1 is completely flow through the feedback component Zf. The input resistance of an amplifier is a very large value. We can write the equation of the input current. The input current I1 is equal to voltage divided by resistance. The voltage coming across Zf is equal to the voltage coming across Zf. We can write the voltage like this. We can take the voltages coming from each terminal. Since the direction of the current is going this way, we can take the voltage here as the high voltage or high potential. We can denote the potential here as Vi. The potential here is minus Vo. That is why the current is flowing this way. The potential coming across Zf is Vi minus Vo divided by Zf. The current Ii is equal to Vi minus Vo divided by Zf. We can write Vo as the gain of the amplifier. Gain is the output divided by input. We can write the output as A into Vi. Or we can write the output as Vo is equal to A into Vi. Instead of Vo, we can substitute A into Vi. We can write it as whole divided by Zf. We can take Vi as common. We can write Vi as 1 minus A divided by Zf. The input impedance of the amplifier is Zi. Zi is the input impedance. Input impedance is the input voltage divided by input current. Input voltage divided by input current is equal to Vi into 1 minus A divided by Zf. We can write Vi by Ii is equal to Zf divided by 1 minus A. We have found the feedback impedance Zf. We have found the effect of this feedback impedance on the input side. The effect of Zf on the input side is Zf divided by 1 minus A. We can write this as equation number 1. We have to find the effect of Zf on the output side. Similarly, assume Io as output current. We assume Io as output current. We assume Io as output current flowing from Vo. Similarly, Io as output current from Vo. We assume Io as output current flowing from Vo. Then, Io is the current flowing across Zf. We have to write the equation for Io as we did for Ii. We have to find the impedance of Vo. Vo divided by Vi is the gain. We have to find the impedance of Vi. the equation of the equation of the equation of the equation of the equation of the equation of the equation of the equation of the equation of the equation of the equation of the equation