Limiting the RF Output power of HMC788A

Document created by analog-archivist Employee on Feb 23, 2016
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We are looking at using the Hittite/ADI amplifier device HMC788ALP2E, but 
biasing voltage available is lower than 5V specified. Do you have any
performance data, especially 1dB power output, at lower than 5V?
We  are interested in limiting the RF O/P Power to +17dBm. Given this fact,we
are trying to apply lower collector bias voltage /Vcc accordingly. Here we need
to check two points-
1. If this is a recommended way of limiting the RF power? If yes, then at what
exact value of Vcc can the limiting requirement can be attained.
2. Frequency of operation is 1GHz-6GHz. However, for their analysis it is
sufficient to provide them P1dB results for the specific Vcc  @1GHz.


Based on the DS, we have had measurement results for the following Vcc settings.

For liming the o/p power up to 17dBm-
When operating the amplifier at Vcc voltage of 3.75 lowered the OP1dB and
supply current to 16.6dBm and ~48mA respectively at 1 GHz. The gain doesn't
change much, although we suspect the IP3 will degrade. In general we think the
approach is ok- it will reduce efficiency but consequently improve
stability..... if you are not considering an option of populating an attenuator
at the output of the amplifier.