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Design >> Analog Design >> stability of the cross-coupled transistor circuit
https://designers-guide.org/forum/YaBB.pl?num=1160577288

Message started by rf_man on Oct 11^th, 2006, 7:34am

Title: stability of the cross-coupled transistor circuit
Post by rf_man on Oct 11^th, 2006, 7:34am

Hi,

Shall the stability of cross-coupled transistor circuit be checked? since this circuit is a positive feedback circuit, it's always instable? Such cross-coupled transistor circuit is often found in many applications, such as frequency dividers, shall a designer ensure that cross-coupled transistor circuit stable? It's really confusing

Title: Re: stability of the cross-coupled transistor circ
Post by loose-electron on Oct 11^th, 2006, 10:32pm

as in a cross coupled load?
or as in a cross coupled latch?
You might want to clarify a bit please, a simple schematic would be great!
tnx,
Jerry

Title: Re: stability of the cross-coupled transistor circ
Post by jbdavid on Oct 11^th, 2006, 10:57pm

How much drive is required to switch them? that might be a good measure of the stability.. if the number drops too close to zero, noise might do the trick!

Title: Re: stability of the cross-coupled transistor circ
Post by rf_man on Oct 12^th, 2006, 12:27am

Thank you for your reply!

I want to know for the following situations.

1. as load of two emitter followers, i.e. the cross-coupled pair is connected to the emitters of the emitter followers.
2. as latch in a D-latch, i.e. the cross-coupled pair connected with a differential pair.

how do you think about the stability issue for the above 2 cases?