need useful references for comparator or S/H design

Circuit desing

i want to design some circuits such as comparator,sample and hold,... but i searched all of my books,all papers and even some thesis nevertheless i couldn't find any thing about circuit sizing(Mosfetes).in all of books only schematic of some circuit presented without any instruction for designing and Mos sizing.
please introduce me some useful references for comparator or S/H design.

Re: Circuit desing

There is no one size fits all for sizing MOSFETS. That is why you generally just FETs shown without the size. The sizing is going to depend on what your circuit needs to do and the process on which you are designing.

Sizing is going to depend on several things like offset, speed and gain of your circuit. If you need a high speed comparator and don't care about offsets you desing with shorter channel lenghts and shorter widths. If you need a low offset comparator you need devices with longer lenghts. So it really depends on what you need your circuit to do to determine how you size devices.

Also, the way you size devices for one process may be totally different when you use another process. You have to read the process manual, which generally includes stuff like mismatch data. You aren't going to find any papers that say this size of device works 100% of the time on every process. Sizing is a huge part of the design and takes work to optimize the values for peak performance.

Circuit desing

Thanks for your reply, I know that sizing of transistors depends on process and several things like offset, speed, resolution. But only in one book I saw some formula for comparator designing that depends on spped, resolution …(in: CMOS Analog Circuit Design, Phillip E.Allen), but unfortunately only Two stage Comparators have been described in this book(with formulas that depend on process).
I want a comprator with this spec:
Gain=1800, Resolution:1mV, Propagation Delay<0.4nS, Vdd=1.8V, ICMR=0-1V, Tech:0.18um
really I mixed up, how can I use of this spec for comparator design?.

Circuit desing

said before the proper size for latch section usually is minimum size. also if possible the size of other sections are minimum for reduced parasitic cap.
about Propagation Delay: Do you say you want a circuit with 2.5GHz speed?

Re: Circuit desing

we can't select minimum sizes for latch components, for example if we use of two stage comparator we must design it according to the formulas for reaching to the specific gain, speed,… (Mentioned in : CMOS Analog Circuit Design.2e.by P.E.Allen).
now it's a question that, how we can use of desired spec(Resolution, offset,..) for comparator design?
not for 2.5GHz.for 1GHz(S/H works with this freq. in Flash ADC):
Ts=1ns→PulseWidth=0.5ns→tp<0.5ns→tp(max)=0.4ns.

Circuit desing

There are no clear synthesis methods in most of analog designs. Only in filters we have strict algorithms and transformations. The rest is computer aided design --- simulations, corrections and so on...

We can try to find some formulas describing some simple circuits, but taking into account all problems and complexity of modern processes... we have a computer simulation only as the most strict methodology.