# Power amplifier delta and K factor <1

1. ## Power amplifier delta and K factor <1

Hello, iam design power amplifier, but my delta and K factor is less than 1 What should I do ?

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2. ## Re: Power amplifier delta and K factor <1

Can you please give us a circuit. Sometimes its hard to translate these questions in English.

3. ## Re: Power amplifier delta and K factor <1

In general people give indication of what their are referring to.
We can assume that you are talking about the loopback gain of a control system.
Being the case, have a look at Barkhausen stability criterion.

4. ## Re: Power amplifier delta and K factor <1

, i would to design the power amplifier with transistor CREE CGH40006S if i want to matching impedance is always not matching ,does it affect the stabilizing circuit? because I just give arbitrary resistive value at the input?

Thanks for your explain, but iam sorry i didnt understand

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5. ## Re: Power amplifier delta and K factor <1

iam sorry i didnt understand
We neither.
Draw some sketch and/or spent more time to depict the "stabilizing circuit".

6. ## Re: Power amplifier delta and K factor <1

Originally Posted by Fhadz
, i would to design the power amplifier with transistor CREE CGH40006S if i want to matching impedance is always not matching ,does it affect the stabilizing circuit? because I just give arbitrary resistive value at the input?

Thanks for your explain, but iam sorry i didnt understand
I did not completely understand your question but I am going to go out on a limb and try to guess it.
So you had a transistor, and you found that your Rollett stability factor is less than 1. And you want to know what to do?
K>1 means unconditionally stable but K<1 does not automatically imply your amplifier is going to be unstable. It depends on your load and source impedance. If your load impedance is fixed, you can draw the load stability circle and see if your amplifier is going to be unstable for the load impedance that you are targeting. If no, then you should be fine.
But if yes, then the only thing you can do it place a series resistor with the gate of your device to reduce the gain and see at what point your load lies outside your load (in)stability circle.

7. ## Re: Power amplifier delta and K factor <1

Originally Posted by vivekroy
I did not completely understand your question but I am going to go out on a limb and try to guess it.
So you had a transistor, and you found that your Rollett stability factor is less than 1. And you want to know what to do?
K>1 means unconditionally stable but K<1 does not automatically imply your amplifier is going to be unstable. It depends on your load and source impedance. If your load impedance is fixed, you can draw the load stability circle and see if your amplifier is going to be unstable for the load impedance that you are targeting. If no, then you should be fine.
But if yes, then the only thing you can do it place a series resistor with the gate of your device to reduce the gain and see at what point your load lies outside your load (in)stability circle.
is the addition of the resistive component the value free without calculation? and I have tried inserting a series resistive component but the MAG becomes small?

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8. ## Re: Power amplifier delta and K factor <1

Originally Posted by Fhadz
is the addition of the resistive component the value free without calculation? and I have tried inserting a series resistive component but the MAG becomes small?
Its kind of hard to do hand calculation. I typically sweep the value of R until I get Kf>1 and I use that value.

But yes indeed, your maximum available gain (MAG) will come down.

9. ## Re: Power amplifier delta and K factor <1

Originally Posted by vivekroy
Its kind of hard to do hand calculation. I typically sweep the value of R until I get Kf>1 and I use that value.

But yes indeed, your maximum available gain (MAG) will come down.
How to use typically sweep the value R in ADS? And the resistif componen always seri ?can i use the pararel?

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