Gate driver design with two branches driving two different transistors

[raguna]

Gate driver design driving two different transistors in each half cycle

Hi all,
Can you help me in designing a gate driver circuit which drives one transistor in half period and other transistor in rest. Design is in AMI 0.5um process.


Thanks

 

[erikl]

Depends if you need non-overlapping clocks or not. If not, you could simply use the same clock signal for both transistors (like in a normal inverter). If the two transistors are connected in series, however - like in a normal inverter - you'll get current shot through during switching, what might not be important for a small inverter, but with such wide transistors could short circuit your power supply or even destroy the transistors. In such case you'd need to use non-overlapping clocks.

 

[raguna]

Hi Erikl!
Thanks for replying to my question. I have two transistors in different blocks which have to be switched at same time. But, after you said, I understood that I need two independent drivers for each of the transistor. Can you help me how I can design two driver circuits driving two different transistors in two different blocks switch at same time. I am not sure how to start with the design.

I considered like the following, please correct me if I am wrong,

Cout=W*L*1.5*2.4fF/um2
Let W=685um, L=0.6u
Cout= 1.477pF

Cin of INVX1=C from PMOS + C from NMOS
Cin of INVX1=(3u*0.6u*1.5*2.4fF/um2)+ (1.5u*0.6u*1.5*2.4fF/um2)
Cin of INVX1=9.72fF

H=Cout/Cin=1.477p/9.72f= 151.44
N=ln(H)= 5, Number of stages= 5
Scale factor= H^(1/N)= 151^(1/5)= 2.72~3

But scale factor of 3 is said be not good, as it is either power loss or slow.
The 5 stages look like 1:3:7:20:55

I wanted to design a low power drivers.

Thanks

 

[erikl]

I have two transistors in different blocks which have to be switched at same time. ... I understood that I need two independent drivers for each of the transistor.

If I understand correctly, both transistors should be "on" (and "off") at the same time? So you need only one driver chain, and one big inverter for the other transistor.

I think 3 inverters (for the inverted signal) and one more inverter (for the non-inverted signal) should be enough for the tapering,
s. e.g. Craig Prunty and Laszlo Gal "Optimum Tapered Buffer", IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 27, NO. 1, JANUARY 1992, p. 118-119.

 

[raguna]

Thanks for your reply. What do you think about scale factor? Do you think what I have done is right in the previous post?

 

[erikl]

What do you think about scale factor? Do you think what I have done is right in the previous post?

Pls. read my answer thoroughly: I think 3 resp. 4 inverters are enough. A scale factor of 3 isn't necessary; a factor of 4..5 is sufficient.
Run transient analyses and compare!

 

[raguna]

Hi all!
I considered an equivalent of two parallel capacitors and does the math. It works fine by doing that.

Thanks all!!