Re: How to amplify 15uV, 1.5MHz signal to read on Scopemeter

Are you considering building a scope preamp to make this adjustment? This
could be a bit more challenging than you think. At 15 uV signal levels, you
have to think about the thermal noise floor. What the source impedance of
the device you're looking at? And what bandwidth (rise time) do you need on
the square wave you're looking at? Calculate the noise floor [sqrt(4KTBR)]
and compare the noise floor to your signal level.

If it's a 50 ohm output, a cheap and easy low-noise preamp is a 50 ohm gain
block like the Minicircuits GALI-39 ($1.19). It's 20 dB of gain (voltage
gain of 10) with 2.4 dB noise figure will get your signal (+ noise) above
the noise floor so you can finish the job with an op-amp. These monolithis
gain blocks are a low cost, low parts count way to go, but with gain well
into the GHz region, you have to know what you're doing layout-wise to make
an amplifier rather than an oscillator.


"JimG" <jggall01@xxxxxxxxx> wrote in message
news:4ck2i3h4sq1bon4aaimhv0drh41tg9hrqc@xxxxxxxxxx
I need some ideas - hope this is the right group.



. . .Doing this requires picking up a 1.5MHz square wave that should have
an amplitude of around 15uV. To see the waveform and adjust the pot I
probably need to amplify this to 5mV, a gain of around 300. . .


.