Peak shunting technique in the high gain amplifier design

[chang830]

peak shunting

In lot of papers, it introduced the peak shunting technique to increase the bandwidth. In pratical designs, it utilize the active inductors load, i.e., a topology which connect a resistor between the supply and mos gate. It indeed exhibite higher bandwidth.

What I want to know, if we target the product design using this technique, what is the disadvantages? I.e., is it feasible to using this technique to develop the commercial product? Can we get high product field?Or will we encounterd some things difficult to control?

Thanks

 

[suria3]

Re: Peak shunting technique in the high gain amplifier desig

Chang,

What speed you are desiging for and with what technology? Active inductor technique will increase the bandwith of an amplifier but it too have some drawback. One of it is the power supply that you provide to the resistor which contribute the inductor effect. Here you need to have 2 power supplies, one is for the MOS another for resistor. So, could be an issue in generating the supply voltages.

Other thing which i could see is, when a signal getting higher and higher, the signal is getting distorted meaning that you will see some ringing or peaking effect of the edges of the upper signal. Although inductor effect will show peaking, but this time it is like more to pulse width distortion and for small swing it is fine. This what i can share with you. Thanks

 

[Teddy]

Re: Peak shunting technique in the high gain amplifier desig

You can use it for sure. there is no issue with yield.
The biggest concern is the Q of the iductor you have and the area of it.
In general it is just a piece of metal in series with the resistor so for lo freqs it behaves like short.

If you will be careful enough you do not have to have even the peaking because you can design the L in a way that it offsets the gain drop of the main circuit. In other words the "flat" gain will be extended.

I know about quite a few products designed with it and there are no issues.
All are dobe for 5GHz and higher

 

[chang830]

Re: Peak shunting technique in the high gain amplifier desig

You can use it for sure. there is no issue with yield.
The biggest concern is the Q of the iductor you have and the area of it.
In general it is just a piece of metal in series with the resistor so for lo freqs it behaves like short.

If you will be careful enough you do not have to have even the peaking because you can design the L in a way that it offsets the gain drop of the main circuit. In other words the "flat" gain will be extended.

I know about quite a few products designed with it and there are no issues.
All are dobe for 5GHz and higher

Hi Teddy,
Thanks for the reply.

"In general it is just a piece of metal in series with the resistor so for lo freqs it behaves like short." Can you elaberate it a bit?

I want to design a 622M limiting amplifier with 0.6um or 0.5um cmos process. So the Q and area is not so critical here with active inductor.

"I know about quite a few products designed with it and there are no issues.
All are dobe for 5GHz and higher"
Would you tell me these product are mainly applifed for?

Thanks

 

[Teddy]

Re: Peak shunting technique in the high gain amplifier desig

Well - in case you will create the coil of metal connected betwen the load resistor and VDD it will for low F work just as a wire. In this case you should make sure that the resistivity of the wire (because it is going to be a long one) is not changing the gain too much. In fact you can make decent resistor from it - (lets say you have sheet R of metal 85mOhm/square and have 100squares you would get 8.5Ohm resistance.
So a little "snaked" structure could make easily 100Ohms.
So for DC and Low F this strip of metal will work just as a resistor. But at higher freq it will have also inductive behavior. Therefore you can design it in to extend your -3dB point

The devices I know of are usually used for high speed data transfer.

I also did a device where I used the inductive behavior of metal to create 50Ohm input across the freq. range.

 

[flushrat]

Re: Peak shunting technique in the high gain amplifier desig

Hi Teddy, do you means use a metal formed inductor? Above which frequency will use inductor? And as I know, sometimes we use active inductor by adding a gate resistor into source follower, what is its frequency range coampared with passive inductor?

 

[elecomm]

Re: Peak shunting technique in the high gain amplifier desig

I also did a device where I used the inductive behavior of metal to create 50Ohm input across the freq. range.

Will you please explain more, I need to know how to get a 50ohm at the input across the frequency range???
thanks