Mar 31, 2017 #1 V venn_ng Member level 5 Joined Mar 26, 2017 Messages 87 Helped 1 Reputation 2 Reaction score 1 Trophy points 18 Activity points 645 Hey guys, I have a question regarding a very simple differential amplifier. I have included the link below. Thanks for your help in advance. **broken link removed** Regards, venn_ng
Hey guys, I have a question regarding a very simple differential amplifier. I have included the link below. Thanks for your help in advance. **broken link removed** Regards, venn_ng
Mar 31, 2017 #2 S shahbaz.ele Advanced Member level 1 Joined Aug 12, 2008 Messages 454 Helped 72 Reputation 146 Reaction score 73 Trophy points 1,308 Location Islamabad, Pakistan Activity points 3,669 It will remain the same.
Mar 31, 2017 #3 pancho_hideboo Advanced Member level 5 Joined Oct 21, 2006 Messages 2,847 Helped 767 Reputation 1,536 Reaction score 733 Trophy points 1,393 Location Real Homeless Activity points 17,490 Effective Rload will be Rd*rds/(Rd+rds). Gain=gm*Rload=gm/(1/Rd+1/rds)=1/{1/(gm*Rd)+1/(gm*rds)}. So Gain is approximated as gm*Rd, since gm*rds >> 1. Last edited by a moderator: Mar 31, 2017
Effective Rload will be Rd*rds/(Rd+rds). Gain=gm*Rload=gm/(1/Rd+1/rds)=1/{1/(gm*Rd)+1/(gm*rds)}. So Gain is approximated as gm*Rd, since gm*rds >> 1.
Mar 31, 2017 #4 V venn_ng Member level 5 Joined Mar 26, 2017 Messages 87 Helped 1 Reputation 2 Reaction score 1 Trophy points 18 Activity points 645 shahbaz.ele said: It will remain the same. Click to expand... Nope. Try deriving using small signal model
shahbaz.ele said: It will remain the same. Click to expand... Nope. Try deriving using small signal model
Mar 31, 2017 #5 V venn_ng Member level 5 Joined Mar 26, 2017 Messages 87 Helped 1 Reputation 2 Reaction score 1 Trophy points 18 Activity points 645 pancho_hideboo said: Effective Rload will be Rd*rds/(Rd+rds). Gain=gm*Rload=gm/(1/Rd+1/rds)=1/{1/(gm*Rd)+1/(gm*rds)}. So Gain is approximated as gm*Rd, since gm*rds >> 1. Click to expand... Ha. It's called "tricky" for a reason. Try deriving using small-signal model using superposition. You will find something different. Last edited by a moderator: Mar 31, 2017
pancho_hideboo said: Effective Rload will be Rd*rds/(Rd+rds). Gain=gm*Rload=gm/(1/Rd+1/rds)=1/{1/(gm*Rd)+1/(gm*rds)}. So Gain is approximated as gm*Rd, since gm*rds >> 1. Click to expand... Ha. It's called "tricky" for a reason. Try deriving using small-signal model using superposition. You will find something different.
Mar 31, 2017 #6 C CataM Advanced Member level 4 Joined Dec 23, 2015 Messages 1,275 Helped 314 Reputation 628 Reaction score 312 Trophy points 83 Location Madrid, Spain Activity points 8,409 venn_ng said: Ha. It's called "tricky" for a reason. Try deriving using small-signal model using superposition. You will find something different. Click to expand... I do not think so.
venn_ng said: Ha. It's called "tricky" for a reason. Try deriving using small-signal model using superposition. You will find something different. Click to expand... I do not think so.
Mar 31, 2017 #7 V venn_ng Member level 5 Joined Mar 26, 2017 Messages 87 Helped 1 Reputation 2 Reaction score 1 Trophy points 18 Activity points 645 CataM said: I do not think so. Click to expand... Why do you think? I am saying that the gain of the circuit is not equal to gm (Rd||rds)
CataM said: I do not think so. Click to expand... Why do you think? I am saying that the gain of the circuit is not equal to gm (Rd||rds)
Apr 1, 2017 #8 V venn_ng Member level 5 Joined Mar 26, 2017 Messages 87 Helped 1 Reputation 2 Reaction score 1 Trophy points 18 Activity points 645 venn_ng said: Why do you think? I am saying that the gain of the circuit is not equal to gm (Rd||rds) Click to expand... I apologize. I confused some weird phenomenon that I observed with this simplistic structure. What you said is correct.
venn_ng said: Why do you think? I am saying that the gain of the circuit is not equal to gm (Rd||rds) Click to expand... I apologize. I confused some weird phenomenon that I observed with this simplistic structure. What you said is correct.