May 30, 2014 #1 A al_dddd Newbie level 6 Joined Aug 31, 2011 Messages 11 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,345 Hi all, Could it be that tha transistor's |s21| is less than 1 (50 Ohms) and still the MAG is high (say 20-22 dB)? How comes?
Hi all, Could it be that tha transistor's |s21| is less than 1 (50 Ohms) and still the MAG is high (say 20-22 dB)? How comes?
May 30, 2014 #2 T Terminator3 Advanced Member level 3 Joined Feb 25, 2012 Messages 802 Helped 71 Reputation 142 Reaction score 63 Trophy points 1,308 Activity points 9,027 Maybe you are looking at wrong s parameters, for different biasing conditions / operation point?
May 30, 2014 #3 B biff44 Advanced Member level 6 Joined Dec 24, 2004 Messages 5,048 Helped 1,376 Reputation 2,748 Reaction score 1,057 Trophy points 1,393 Location New England, USA Activity points 37,918 Of course, provided that S11 and S22 magnitudes are large, and you design a low loss matching network for both. Back in the day, it was COMMON for a S21 magnitude to be pretty poor! We got along somehow.
Of course, provided that S11 and S22 magnitudes are large, and you design a low loss matching network for both. Back in the day, it was COMMON for a S21 magnitude to be pretty poor! We got along somehow.
May 30, 2014 #4 A al_dddd Newbie level 6 Joined Aug 31, 2011 Messages 11 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,345 Terminator3 said: Maybe you are looking at wrong s parameters, for different biasing conditions / operation point? Click to expand... Just took transistor sith dc blocks and feeds and plotted s21 and MAG... s21 is beliw 0db while mag is about 18dB. Same bias of course.
Terminator3 said: Maybe you are looking at wrong s parameters, for different biasing conditions / operation point? Click to expand... Just took transistor sith dc blocks and feeds and plotted s21 and MAG... s21 is beliw 0db while mag is about 18dB. Same bias of course.
May 30, 2014 #5 BigBoss Advanced Member level 6 Joined Nov 17, 2001 Messages 5,977 Helped 1,610 Reputation 3,227 Reaction score 1,596 Trophy points 1,393 Location Türkiye Activity points 35,918 al_dddd said: Just took transistor sith dc blocks and feeds and plotted s21 and MAG... s21 is beliw 0db while mag is about 18dB. Same bias of course. Click to expand... MAG is depending on the Stability Factor.If K<<1, even dB(S(2,1))=1 MAG(dB) can be >>1. K factor is important in definition of MAG.
al_dddd said: Just took transistor sith dc blocks and feeds and plotted s21 and MAG... s21 is beliw 0db while mag is about 18dB. Same bias of course. Click to expand... MAG is depending on the Stability Factor.If K<<1, even dB(S(2,1))=1 MAG(dB) can be >>1. K factor is important in definition of MAG.
May 31, 2014 #6 A al_dddd Newbie level 6 Joined Aug 31, 2011 Messages 11 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,345 BigBoss said: MAG is depending on the Stability Factor.If K<<1, even dB(S(2,1))=1 MAG(dB) can be >>1. K factor is important in definition of MAG. Click to expand... So that means that while transistor is unstable the mag could be positive while the s21 negative? Mag btw is not well defined for negative k since it has sqrt (k-1) term...if I remember correctly. - - - Updated - - - biff44 said: Of course, provided that S11 and S22 magnitudes are large, and you design a low loss matching network for both. Back in the day, it was COMMON for a S21 magnitude to be pretty poor! We got along somehow. Click to expand... Can you elaborate a little? Just give an intuition of that- s11 and s22 are large and the gain is large despite poor s21...
BigBoss said: MAG is depending on the Stability Factor.If K<<1, even dB(S(2,1))=1 MAG(dB) can be >>1. K factor is important in definition of MAG. Click to expand... So that means that while transistor is unstable the mag could be positive while the s21 negative? Mag btw is not well defined for negative k since it has sqrt (k-1) term...if I remember correctly. - - - Updated - - - biff44 said: Of course, provided that S11 and S22 magnitudes are large, and you design a low loss matching network for both. Back in the day, it was COMMON for a S21 magnitude to be pretty poor! We got along somehow. Click to expand... Can you elaborate a little? Just give an intuition of that- s11 and s22 are large and the gain is large despite poor s21...
Jun 5, 2014 #7 A al_dddd Newbie level 6 Joined Aug 31, 2011 Messages 11 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,345 Push it up...