how to remove the poles of a gain boosted amplifier.

[shrikant_joshi7]

i am designing a gain boosted amplifier and the gain is not high.all the transistors are in saturation.i am using simple differential amplifiers as auxiliary amplifiers.The gain i am getting is 76dB with UGF of 700Mhz but the UGF<PCF so the system is unstable even in open loop configuration,It is because of a no. of poles at the nodes where the auxiliary amplifiers are connected.

How can i increase the gain of gain boosted amplifier?
How to remove these unnecessary poles?

 

[kemiyun]

You cannot remove poles. But you can compensate those poles which is not a very efficient solution. A better solution is to make those gain boost amplifiers excess stable as said in Vadim Ivanov's book. If you are compensating you are reducing the speed that you have already paid for with power by using capacitors which is equal to area. Use only one high impedance node at the gain boost amplifiers.

First way to increase the gain of a gain boosted amplifier is to use source bulk connection for cascoding transistors if the process allows it. This decreases the effects of impact ionization. In AMS0.35 it was quite important. You can also use better schemes for gain boost. There are many proposed architectures, there are even gain boosted gain boost amplifiers . Using simple differential amplifiers, depending on your configuration, might decrease your output range.

 

[wulong527]

If it is ture that "it is because of a no. of poles at nodes where the auxiliary amplifiers are connected, lower the UGF of auxiliary amplifier or higher the second pole of main amplifer. To make it more clearly, it's better to give out the performance metric of your main amplifier and auxiliary amplifer .