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Measurements >> RF Measurements >> Ac parameter measurement
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Message started by summi on Dec 23^rd, 2012, 2:25am

Title: Ac parameter measurement
Post by summi on Dec 23^rd, 2012, 2:25am

dear forum,
Can any one please tell me how to measure small signal parameters like opamp gain,BW or LDO psrr in lab. First thing coming to my mind is VNA, but since analog circuits don't have 50ohm impedance i don't think it will be useful.

Br,
Summi.

Title: Re: Ac parameter measurement
Post by MikeL on Jan 18^th, 2013, 2:27am

Start by defining what sort of gain your op-amp circuit is providing: usually it is voltage gain but it could be configured to provide current gain or current to voltage conversion. Then put a known signal in one end and measure the output signal - this gives you the gain.

You could use a signal generator for the input and an oscilloscope to measure the output. Vary the frequency of the input signal and see how the gain varies... this allows you to measure bandwidth.

With all measurements, it is best to define what you expect before you start. I have no idea what LDO psrr is - but if you can describe how you expect this to vary then you are halfway to defining the measurement.

You could probably use a VNA to do all of this, but unless you have designed your measurement the VNA will just generate rubbish but on a very pretty display!