CMOS opamplifier Design in 0.18micron technology

[calculus_cuthbert]

CMOS Amplifier Design

Hi,

I need to design a differential to single ended amplifier with negative feedback (to control the gain). The input is a differential signal so i need both terminals

The simplest would be a diff pair but how do i implement negative feedback because i need to use both the input terminals?


I thought about a few options:

1. Designing an opamp and then using resistors to build a difference amplifier
2. The input impedance may be a problem if i use a difference amplifier, so may i need to design an instrumentation amplifier.

Is there a more elegant way to implement controllable gain differential to single ended converter?

I need to start designing soon, I would really appreciate if someone could suggest ideas.

Thank you.

 

[JoannesPaulus]

CMOS Amplifier Design

I would design the buffer with two amplifiers: the first one implements the gain (fully-differential to fully-differential), the second one does the fully-differential to single-ended conversion.

 

[calculus_cuthbert]

Re: CMOS Amplifier Design

Hi,

Thank you for your reply. Could you explain in a little more detail please? i didn't quite follow your suggestion.

Another thing to add is that the differential signals are pretty high, the amplitude is 300mV and I don't want too much gain.. ideally around 15dB

Also in order to control the gain I would require some kind of negative feedback. How do I implement this feedback if I have differential signals?

 

[strabush]

Re: CMOS Amplifier Design

Look up at the block diagram of an Instrumentation amplifier. (Google it up)

 

[JoannesPaulus]

CMOS Amplifier Design

check http://www.ecircuitcenter.com/Circuits/adcin_fully_diff/adcin_fully_diff1.htm
for the fully-differential amplifier and
http://www.ecircuitcenter.com/Circuits/adcin_diff_se/adcin_diff_se1.htm
for the fully-differential to single-ended amplifier.

Added after 30 minutes:

there should not be any problem to have 15db gain (1.7V output). A fully-differential folded-cascode amplifier is my recommendation (for the first amplifier).

 

[uddin.ammad]

CMOS Amplifier Design design in 0.18micron technology

hello
i need a 2-stage cmos opamp design in 0.18u technology.............
is there any body to help me