I plan to use the MAX2606 (or 2607) to provide the AC source for an AC bridge circuit (schematic attached). The difference between the two capacitors in the bridge will be measured using a simple diode detector network.

1. Since the MAX VCO has a differential output, can I connect it directly to the bridge circuit, or should I use a transformer (like I have done in the schematic)?

I understand that the output power of the MAX VCO is -8dBm which (I think) equates to ~89mV RMS through a 50ohm load
2a . How do I increase the voltage through the bridge to be detected by the diode detector? Take a single ended output and amplify it?

The MAXIM application note (https://www.maximintegrated.com/en/design/technical-documents/app-notes/3/3633.html) talks about how they used pull-up inductors instead of resistors to increase the voltage swing (which is what they did on the evaluation kits), and page 12 of the datasheet (https://datasheets.maximintegrated.com/en/ds/MAX2605-MAX2609.pdf) recommends using an LC network to increase the voltage swing, but the values are chosen according to the load impedance -
2b. If I use a transformer to couple the VCO and bridge - should the transformer have an impedance of ~50ohms at the chosen frequency?

 

hi tal,
The MAX d/s states that the outputs are open collector, so where on your diagram are using pull ups to get the required voltage swing.?
E

 

V1 in my schematic is a stand-in for what will one-day be the MAX260x VCO. I haven't got the VCO on my schematic, so I haven't shown the pull-ups.
I am aware that the datasheet and application note refer to the use of pull-up inductors instead of resistors for high frequency operation, but am unsure on how exactly they chose the values of the LC networks.