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How to bias a MOSFET for 1W push pull amplifier?

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jeeves

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Hi people,

I tried posting in the Analog Circuit Design but I got no replies :cry:

Anyways, I'm trying to design the output stage of a 1 Watt push pull amplifier using dual NPN RF MOSFET at 40MHz and a 24 Volt single supply. I'm not using any inductors or transformers. I'm not sure how to bias the MOSFET correctly. What type of biasing circuit should I be using ?

Since, I've got a single supply, does that mean I gotta operate the MOSFETs in Class A Push Pull?

Thanks,
Jeeves
 

push pull mosfet

the way you have biased the circuit is right only also the MOSFET is stable even through temperature changes....
i think you have to be careful in the selection of resistors and caps to be used....
 

mosfet push pull

Thanks for the reply A.Anand Srinivasan.

I'm having problems with biasing the circuit. I seem to get both NPNs on at the same time and shorting to ground. How do I set the DC voltage point which the mosfet will swing about ?
 

mosfet push pull amplifier

i thought you were using a MOSFET.... if you are using NPN then you basic circuit itself is wrong..... the lower transistor is supposed to be a PNP...
 

mosfet push-pull

I'm trying to design it using two NPN in common source config and drive it using split phase. Is this possible ?
 

mosfet push pull circuits

jeeves said:
I'm trying to design it using two NPN in common source config and drive it using split phase. Is this possible ?
Click to expand...


NPN is a BJT and it doesnt have a common source configuration... can you be specific about whether you are using a BJT or a MOSFET.....

your circuit diagram suggests MOSFETs but you are talking in terms of BJT(NPN)...
 

push pull mosfet amplifier

For this type of Confugaration Both NPN transistors doent work, because on transistor is in CS confugaration other is in Source follower Confugaration and Outputs amplitudes will not be same and they are out of phase.

If you want to try with all N-transistor Try input Vina Should first go to a source follower M3 than connect this output to M1 in this way all NPN configuration is possible with 3-NPN transistors
 

push-pull mosfet

My apologizes, I meant N-Enhancement MOSFETS, I don't know why I refered to them as NPN. :|

Thanks, Raj, I'll give that a shot.
 

push pull amplifier for mosfet

Sorry a mistake ... connect M3 as CS amplifier
 

mosfet push pull

invert your NMOS M2 i.e connect source where drain is connected now and drain where source is connected now... replace M1 with a PMOS with drain connected to resistor and source to supply...
 

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