> Is the IP3 spec referred to input or output?
> The 1 dB compression spec (+15 dBm) does not make sense in
> light of the 20 dB gain spec. It implies that you can get
> +34 dBm out if you put +15 dBm in. +34 dBm is 2.5 watts.
> Also, it would be useful to know the IP2 spec.
> Thanks,
>
> Rick N6RK
---
I'm also interested in hearing about the input IP3 performance.
The new InGaP HBT MMICs are interesting because they can run more power and
have lower 1/f noise than earlier GaAs MESFET amps.
So far, I have not used these GaAs MMICs because they are still short of
discrete design performance. All devices I know of specify output IP3
performance, with input IP3 being lower by the amount of gain. Thus, a +35
dBm IP3, 20 dB gain spec corresponds to an IIP3 of +15 dBm, which is not
bad, being about the same as a typical diode double-balanced mixer.
Similarly, the 1dB compression point will also be an output specification.
For comparison, the classic negative feedback 2N3866 circuit I use in my
preamps has around +30 dBm input IP3 with 60 mA bias. Two of these amps in
push-pull, and biased a bit stiffer can deliver input IP3 exceeding +40 dBm.
73, Gary
K9AY
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|