greenjuice
Member level 1
Self Biased(regulation) circuit problem due to both positive and negative loops
Hello. I am trying to design traditional self-biased voltage reference.
as you can see attached picture, it has positive and negative loops at the same time.
to realize this circuit, i should make negative loop gain get stronger than positive loop gain.
loop gain of rightward loop(negative loop)
= gm1 * A(amp gain) * (R1 + rQ1)/(R1 + rQ1 + R2A)
loop gain of leftward loop(positive loop)
= gm2 * A(amp gain) * rQ2/(rQ2 + R2B)
Assumption that gm1 = gm2
then, to make negative loop stronger we should follow this
: (R1 + rQ1)/(R1 + rQ1 + R2A) > rQ2/(rQ2 + R2B)
it means feedback factor should determine our loop stability.
it's my own conclusion. so is it right?
i'm not sure
please give your advice.
Thank you beforehand
Hello. I am trying to design traditional self-biased voltage reference.
as you can see attached picture, it has positive and negative loops at the same time.
to realize this circuit, i should make negative loop gain get stronger than positive loop gain.
loop gain of rightward loop(negative loop)
= gm1 * A(amp gain) * (R1 + rQ1)/(R1 + rQ1 + R2A)
loop gain of leftward loop(positive loop)
= gm2 * A(amp gain) * rQ2/(rQ2 + R2B)
Assumption that gm1 = gm2
then, to make negative loop stronger we should follow this
: (R1 + rQ1)/(R1 + rQ1 + R2A) > rQ2/(rQ2 + R2B)
it means feedback factor should determine our loop stability.
it's my own conclusion. so is it right?
i'm not sure
please give your advice.
Thank you beforehand