op-amp with gain>60db

[elmasso]

hi i have a homework that want me to design a op-amp with these specs :

single ended output and gain greater than 60db
capacitor load 1pf
Vdd = 3.3v
output swing > 2.4v
ugf>200MHz
Slew Rate > 400v/us
power<6mW
phase margin >60 degrees

it would be great help if someone can help me with design or introduce me some sources ASAP

 

[Audioguru]

I think your homework is to design an impossible circuit.

 

[erikl]

... introduce me some sources

I think it's not impossible, but challenging. You'll need at least 400µA in the output stage(s).

Read chap. 5: Design of CMOS Operational Transconductance Amplifiers Optimized for DC, Balanced, and AC Performance from David M. Binkley's book "Tradeoffs and Optimization in Analog CMOS Design"

 

[Dominik Przyborowski]

You'll need at least 400µA in the output stage(s).

But He has almost 2mA to use and only 1pF of load capacitance. Many options should works.

 

[tompham]

Hi elmasso

Use folded cascode with tail current and 2 legs > 400uA you can do it

 

[schmitt trigger]

The question is: is the 1pF load realistic at all?
This is way too low. Almost anything that you put on the output will have at least a few pF.

 

[erikl]

Almost anything that you put on the output will have at least a few pF.

Not, if it is a CMOS gate again, e.g. an output amplifier on the same chip.

 

[schmitt trigger]

Not, if it is a CMOS gate again, e.g. an output amplifier on the same chip.

You are absolutely correct,
but unfortunately the poster's original requirements left this open to interpretation.