Hello AD,
I would like to be able to enable/disable an individual HMC8413 RF amplifier without changing its RF characteristics while introducing zero (or an absolute minimum) of added noise into my signal path. I have come up with the scheme shown below and want to run it past the experts at AD to see if they think it will work.
In words what I am doing is placing a SPST analog switch (ADG801) in series with the Rbias resistor that is nominally 787 ohms. The switch is controlled with a CMOS logic level and is assumed to be operated in an ON/OFF - very, very low bandwidth - configuration. When the switch is ON it adds less than an ohm of resistance to Rbias and the HMC8413 should operate normally with a 95 mA DC bias current from a 5V supply. When the switch is OFF it should effectively raise the Rbias value to several mega-ohms thus reducing the amplifier bias current to something less than 20 mA (or ideally 0) and effectively disabling it's operation and hence current consumption, heating, etc. When the amplifier is disabled there will be no RF input signal and its output is ignored.
Schematically it looks like this:
My questions are:
1. Will this work in Enabling/Disabling the amplifier?
2. Do you see any adverse effects to the noise performance of the amplifier (noise figure, OIP3) when the amplifier is enabled?
Thank you,
Tony
