How to design output buffer in 8GHz divider by2

[2steps]

Hi, All:


Recently, my task is to design a 8GHz divider by2. I think it is easy to design divider core circuit, but I do not know how to design output buffer to drive 50ohm test probe.
You konw, It is very sensitivity to output parasitic resistors and capacitors.I want to test this divider on wafer by GSG probe.
Thanks!

 

[master_picengineer]

How to design outpubuffer in 8GHz divider by2

Hi,
Please could you please through more ligth (Analog design of Digital). At which level you design the divider (gate /transistor). What technology you use CMOS, bicmos.
Thanks.

 

[Mazz]

How to design outpubuffer in 8GHz divider by2

It depends on the design of the divider.
Is CMOS or ECL, single end or differential?
Mazz

 

[khouly]

How to design outpubuffer in 8GHz divider by2

u may use something like cherry hopper feedback buffer , it can be used , use this buffer used CML for high speed operation

khouly

 

[2steps]

How to design outpubuffer in 8GHz divider by2

Hi,

1.This divider's deisgn is based on 0.18um Mixed Signal/RF CMOS.
2. The divider is based on D filp-flop,realized using CML(current mode logic). and its input and output are differnential.

3. This figure is output buffer schematic from a paper, it is used to create sufficient output voltage swing, it consists a source follower and two amplifier stage
But I doubt its bandwidth and stability, please help to check it.


.

 

[Mazz]

I do not see any stability issue, there is no feedback.
How much gain do you need from the two stages amplifier?
How do you think to convert the differential signal to single end?
There could be bandwidth limitation, but it depends on current used and on parasitics in high impedance nodes (mainly loads of the amplifiers).
I think you know that it is absolutely desiderable to make the measurement in a matched condition to avoid reflections.
In any case, supposing that the GSG will be seen from the circuit as a 50 Ohm load, the latest load resistor has to be 50 ohm too (and the simulations have to be done with the external load inserted).
I hope it can help.
Mazz