When compared to standard cascode, folded cascode is a single gain stage where as normal cascode is not. So folded cascode allows a more direct signal path.
For instance, if you have 20dB of gain , then the output should be good for 20Vrms hence the high rails. I think we should make this preamp quite flexible and this amount of gain could be quite useful for SE MOSFET Follower amps.
For instance, if you have 20dB of gain , then the output should be good for 20Vrms hence the high rails. I think we should make this preamp quite flexible and this amount of gain could be quite useful for SE MOSFET Follower amps.
When compared to standard cascode, folded cascode is a single gain stage where as nor
Oh I see...... that clears that up. Maybe you can post a schematic of each casode type and explain it in terms of voltage gain, load resistance, input device transconductance,PSRR, and device count. We would all like to learn how to design folded cascodes if they are better than conventional cascodes. Actually there is an important difference between the two.
H.H.
Oh I see...... that clears that up. Maybe you can post a schematic of each casode type and explain it in terms of voltage gain, load resistance, input device transconductance,PSRR, and device count. We would all like to learn how to design folded cascodes if they are better than conventional cascodes. Actually there is an important difference between the two.
H.H.
Harry,
There are a few people here that know what they are on about when it comes to various cascode circuits. Sorry but i dont have the time to do a full run down at the moment as my EE studies are piling up in the corner. Hopefully someone else will do so on my behalf. It sounds like you have your own comments "there is an important difference......." please dont hold back we are all here to learn from each other.
There are a few people here that know what they are on about when it comes to various cascode circuits. Sorry but i dont have the time to do a full run down at the moment as my EE studies are piling up in the corner. Hopefully someone else will do so on my behalf. It sounds like you have your own comments "there is an important difference......." please dont hold back we are all here to learn from each other.
a few people here that know what they are on about when it comes to various cascode c
That's OK we will wait until you have time. I wouldn't want anyone to put words in your mouth or do a poorer job explaining it than you would. I, and I am sure others, would really like to know. At your convienance, and thanks for an interesting new topic.
H.H.
That's OK we will wait until you have time. I wouldn't want anyone to put words in your mouth or do a poorer job explaining it than you would. I, and I am sure others, would really like to know. At your convienance, and thanks for an interesting new topic.
H.H.
"an interesting new topic"
HH,
Cascodes have been discussed to death it is not what i would call an interesting new topic. 🙂 I dont mind if someone else goes over the theory, it's far quicker for me to post corrections/disagreeances than to go thru the whole thing.
HH,
Cascodes have been discussed to death it is not what i would call an interesting new topic. 🙂 I dont mind if someone else goes over the theory, it's far quicker for me to post corrections/disagreeances than to go thru the whole thing.
i have an excellent explanation of folded cascode amps in my analog textbook, with comparisons to a regular cascode, but it is long and involved with lots of diagrams, and i am too dumb to summarize it properly... 🙁
i was going to scan it but i don't have a proper scanner on me. i have a nice digital camera but the macro capability is somewhat limited. i'll see what i can do.
anyway, go study. you don't want to end up like i did in EE401 senior year (analog circuits), playing video games all night instead of doing my problem sets (that's what they call "homework" over here so we don't feel like we're in grade school anymore). my teacher, a designer at Analog Devices, very nice fellow, liked me a lot, but didn't quite understand me and my slacker mentality. my old roommate and fellow EE spoke to him once recently:
"Yeah, i never understood your friend Marc. I liked the guy and he seemed bright. But then he would walk into my mid-term, and announce, 'I'm going to fail this mid-term.' and sure enough, he failed it. What was I supposed to do?"
anyway, go study. you don't want to end up like i did in EE401 senior year (analog circuits), playing video games all night instead of doing my problem sets (that's what they call "homework" over here so we don't feel like we're in grade school anymore). my teacher, a designer at Analog Devices, very nice fellow, liked me a lot, but didn't quite understand me and my slacker mentality. my old roommate and fellow EE spoke to him once recently:
"Yeah, i never understood your friend Marc. I liked the guy and he seemed bright. But then he would walk into my mid-term, and announce, 'I'm going to fail this mid-term.' and sure enough, he failed it. What was I supposed to do?"
i dunno about you guys, but i am going to try the latest borberly circuit, the DC-coupled complementary one. i may try to go w/o the DC servo if i can get away with it, probably not though...
oh. crap. i forgot about that. hmm.
i don't know. i'm torn. i really like that one but like you said it is not balanced and it is not SE either, which you guys seem to really love. i dunno. what should i do? 🙁
i don't know. i'm torn. i really like that one but like you said it is not balanced and it is not SE either, which you guys seem to really love. i dunno. what should i do? 🙁
If we use the circuit that i suggested, there will be single ended and balanced inputs and outputs. Also it is balanced SE thru-out.
If it's not too much trouble, please post the book title and pages. I am like Harry in the regard that I would like to understand something that perhaps I do not.
mlloyd1
mlloyd1
dorkus said:
Read thru the last few pages....
Folded cascode LTP JFET input with SE Class A mosfet follower outputs. Digital volume control located between stages. No negative feedback and use degeneration to gain decent specs. Rails would be at least +/- 50V.
JFet (2sk389) for the diff amp input pair.
MOSFET for the cascode.
BJT current sources where required and passive resistor bias elsewhere.
Folded cascode LTP JFET input with SE Class A mosfet follower outputs. Digital volume control located between stages. No negative feedback and use degeneration to gain decent specs. Rails would be at least +/- 50V.
JFet (2sk389) for the diff amp input pair.
MOSFET for the cascode.
BJT current sources where required and passive resistor bias elsewhere.
It seemed like we were starting to converge on the Borbely-like JFET diff amp with someone's (Jam maybe?) suggestion of MOSFET source follower outputs (instead of Borbely's complementary JFETs)?
10V across the JFETs if you cascode. +/-24V rails. Run the MOSFETs "hot" (50mA?).
Yes???
mlloyd1
10V across the JFETs if you cascode. +/-24V rails. Run the MOSFETs "hot" (50mA?).
Yes???
mlloyd1
dorkus said:
And I think we should stick to that. Although "newer" Borberly circuit is tempting because of no DC output, it's no good for balanced operation. I still think that circuit is 15 years old. Substitution of transistors doesn't change much. When I was building my preamp in 1992 I chose A75 front end over Borberly circuit. Nelson Pass approach seemed nicer to me.
mlloyd1,
For understanding folded cascode I suggest you read A75 article starting from page6: http://passdiy.com/legacy.htm😉
mlloyd1,
For understanding folded cascode I suggest you read A75 article starting from page6: http://passdiy.com/legacy.htm😉
Convergence?
JFet for the diff amp input pair. yes
MOSFET for the cascode. yes
Folded cascode will complicate circuit. no
50V rails. No way, how about 25volts
Single ended Mosfet followers. yes
Ac coupled outputs. yes
Balanced in and out. yes
This is possible with a fairly simple fet circuit. All in favor say Aye.
Gentlemen?
JFet for the diff amp input pair. yes
MOSFET for the cascode. yes
Folded cascode will complicate circuit. no
50V rails. No way, how about 25volts
Single ended Mosfet followers. yes
Ac coupled outputs. yes
Balanced in and out. yes
This is possible with a fairly simple fet circuit. All in favor say Aye.
Gentlemen?
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