Outamp Prototype - WCP52/docs GitHub Wiki

Git repository: WCP52/outputamp

Out output amplifier must take small signals, at -8.5 dBm as they arrive from the synthesizer, and output the full 15 dBm signal. For design margin, a 16.5 dBm output amplitude is assumed. This gives a required gain of 25 dB. An additional 6 dB gain is requiredto compensate for the insertion loss of the termination, giving a total required gain of 31 dB.

A gain of 31 dB from 1 kHz (practically DC) to 150 MHz is difficult to achieve, particularly with the very large absolute amplitude of 21 dBm at the output. We chose to use two gain stages of 15.5 dB each. The final stage is a THS3001 operational amplifier, as it supports the high slew rate, high voltage and high output current required. This is a very expensive amplifier, though, so we used the AD8000 (similar specifiations, but with a lower maximum supply voltage) for the first stage.

The synthesizer allows amplitude control, but this control is applied at the digital stage, resulting in a loss of DAC resolution. To get more range at full resolution, we included a MAADSS0008 switchable 15 dB attenuator in the output amplifier's signal path.

Layer renders: top, inner2, inner3, bottom