Folded Cascodish

Tim__x · 17th October 2005, 10:23 PM

I just came up with this, it's basically a folded cascode with single transistor input instead of a LTP. Does it have a name?

hjelm · 18th October 2005, 12:36 PM

Wont you get a negative Vbe as it is drawn today, or does it pull an offset current out of the source via the feedback?

Suggest you put the emitter of the input transistor below 0V. I assume also that you will get clipping at ~0.7 Vpp in?

bocka · 18th October 2005, 03:14 PM

Quote:

Suggest you put the emitter of the input transistor below 0V.

No. It should work fine. The feedback biases Q1. Current through Q1 will be about 0.9mA. DC output offset is 1 + 20k/10k * Vbe = 1.8V.

Christer · 18th October 2005, 04:28 PM

I think what you have drawn actually is a proper folded cascode. Although folded cascodes are commonly used together with diff pairs, there is nothing in the name itself to suggest it must be applied to diff pairs. If you search on "folded cascodes" on the forum you will find plenty of examples of people calling "your" circuit a folded cascode.

Tim__x · 18th October 2005, 06:06 PM

Thanks Christer.
I didn't think it could possibly be new. Do you know of any commercial designs using it?

18th October 2005, 12:36 PM	#2
hjelm diyAudio Member Join Date: Nov 2003 Location: Västerås	Wont you get a negative Vbe as it is drawn today, or does it pull an offset current out of the source via the feedback? Suggest you put the emitter of the input transistor below 0V. I assume also that you will get clipping at ~0.7 Vpp in? __________________ Hjelm

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18th October 2005, 04:28 PM	#4
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	I think what you have drawn actually is a proper folded cascode. Although folded cascodes are commonly used together with diff pairs, there is nothing in the name itself to suggest it must be applied to diff pairs. If you search on "folded cascodes" on the forum you will find plenty of examples of people calling "your" circuit a folded cascode.

18th October 2005, 06:06 PM	#5
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	Thanks Christer. I didn't think it could possibly be new. Do you know of any commercial designs using it?

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