Re: Critique requested for circuit design

Thanks I'll have a re-think about the whole circuit.
Looking at it now it looks like crap!!

Kevin.
"Andrew Holme" <ajholme@xxxxxxxxxxx> wrote in message
news:1121271209.247874.313550@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
>
> Kevin Doyle wrote:
>> Hi all,
>> Here I have a circuit diagram of an FM 106Mhz transmitter I built.
>> http://homepage.eircom.net/~doylekevin/fm-tx.jpg
>> I dont think I'm maximising the potential of the bfg 235 transistors. If
>> you
>> could take a look at it and suggest any modifications I would be
>> greatful.
>> Cheers,
>> Kevin.
>
> You need some sort of matching network at the output. You can't just
> hang a 50 ohm load off the end of C14.
>
> How did you arrive at the figure for output power?
>
> R12 looks a bit on the large side for the job it's doing.
>
> You don't show any power supply decoupling in the diagram.
>
> That 3dB pad is only a 3dB attenuator when it's input and output are
> both terminated in 50 ohms.
>
> The other inter-stage coupling networks are unusual. I presume you are
> controlling the drive level by adjusting the value of U2 and U3?
>
> You seem to have a lot of gain in the driver stage. I wonder if it
> would be safer to give some of it to the "buffer" stage.
>


.

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