Hi,

In order to properly answer this question, you must give more information. In what set-up do you measure your chip: package, chip-on-board, wafer probing? Will you be able to use high-impedance probes (take care, their bandwidth is usually limited) or will you have 50-Ohm equipement (typical for RF measurements).

In the latter case, you cannot attach the measurement equipment directly to your amplifier output, except it has low-impedance output. Single-stage amplifiers usually are OTAs, not opamps and cannot drive such a low-impedance load. You need a buffer stage in between the OTA and the 50-Ohm equipment.

To simulate this, you simply have to include a model of the measurement equipment, typically a load resistor to ground with a load capacitor in parallel. You find the values for these components in your probe/scope data sheet.

Paul

If you work in a 50-Ohm environment, impedance matching should be guaranteed, but further more you have to simulate your circuit with the load. The resistive load may modify the operating point of your circuit, so be careful.

Regarding probing, you can use differential RF probes to directly sense the differential signal going off the chip, but this usually requires two scope channels. Converting it to single-ended eases the set-up but cancels the advantages of differential signalling.

Paul