HP 33120A 15Mhz Function Generator square wave

[Helix70]

Hi Guys,

I have an HP 33120A 15Mhz function generator. I was trying the square wave output into a 50 ohm load at the DSO (output set to 50 Ohms also, 1V p/p) and it looks pretty rubbish at higher frequencies.

Is this the same for others, or is mine broken? Below is 1Mhz, 10Mhz and 15Mhz respectively. Looks like the output filter is in circuit, but why for a square wave?

Josh

[capt bullshot]

Mine looks basically the same. The output amplifier isn't fast enough for a 15MHz square wave. You'll find that behaviour on many function gens, the highest frequency square wave looking more like a sine.

[David Hess]

That sort of performance when making square waves is typical for a function generator because of limitations in the linear output amplifer.  A pulse generator is more suitable if you require cleaner square waves.

[Helix70]

Thanks Guys. I mainly use it for sine waves and the odd arb, but was trying to use it for a clock on a micro. Might need a comparator to square it up a bit.

[capt bullshot]

Just use the sync output for that.

[Helix70]

Great idea. I just tried it and thats a good solution. I will need to deal with the amplitude as it is fixed between 3 and 4.5 volts, but even the duty cycle works.