Electronics > Projects, Designs, and Technical Stuff
Increase amplitude range of a function generator
gkmaia:
I am trying to figure out what is the best way to increase the amplitude range of an HP 3311 function generator.
The output amplifier ranges between -18/+18v based on it's supply.
If I were to increase it's range 10 fold to -180/+180 what would be the best approach? Modify the circuit? A step up high frequency transformer on the output?
gbaddeley:
Use an external amplifier that meets slew rate, frequency range, and output current requirements.
A transformer may work under light load conditions, because it also increases the source impedance by square of turns ratio. Sine may be OK, square & triangle will be distorted.
bitseeker:
I second the external amplifier recommendation. :-+
duak:
I believe the hp 3311A has a maximum frequency of 1 MHz. There's a discussion in this thread on an amplifier with similar voltage & frequency chc's: https://www.eevblog.com/forum/projects/analog-challengehigh-powerhigh-speed-amplifier-for-physics-experiment/ Its output current is probably higher than what is wanted but it's easier to decrease rather than increase it.
Cheers,
nfmax:
The 3311A output stage is designed for a 600 ohm load, not the usual 50 ohm. I believe it will swing +/- 10V into this load. Stepping up to +/- 100V using a transformer would only work (well) for a load of 60 kohm or more. This may be OK for you, although finding a suitable transformer may be difficult.
Edit: it looks like its only +/-5V into 600 ohms
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