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Tips about this circuit ?
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Gregory:
Hello guys! I designed and tested this 10Mhz amplifier, filter and buffer.
The idea is that a 10Mhz signal from a Rubidium Standard comes in and the crystal filter and buffer output stages will be replicated 6 times for 6 output channels.
I prototyped this circuit and it appears to work really well.
Do you have tips for improvement?
thank you!
bob91343:
Input and output impedance and levels? Pic of waveform?
If you are doing this six times, the input impedance has to be 6 times higher to avoid overloading the source.
dom0:
The absurdly high Q value of the quartz circuits can pull the average output frequency from the mean value at the input. I think these can be used, but you would have to reduce their Q considerably (dampen the crystals with a resistor of a couple hundred Ohms across them).
ArthurDent:
You might want to check what has already been done in the past to get ideas. A number of frequency standards used xtal filter/buffers on the output of their oscillators, like this HP schematic shown. The manuals quite often has a section on theory of operation that might be useful.
Gregory:
--- Quote ---Input and output impedance and levels? Pic of waveform?
If you are doing this six times, the input impedance has to be 6 times higher to avoid overloading the source.
--- End quote ---
The output impedancia of the standard is ~50ohm. The output of my circuit is ~50ohm through the 47ohm output resistor.
The follower stage after the comom emitter stage generate the low impedance signal to drive the 6 crystal filters.
The input has 3.5Vpp and the output 2.4Vpp (~11dbm on 50ohm)
--- Quote ---The absurdly high Q value of the quartz circuits can pull the average output frequency from the mean value at the input. I think these can be used, but you would have to reduce their Q considerably (dampen the crystals with a resistor of a couple hundred Ohms across them).
--- End quote ---
Why?
--- Quote ---You might want to check what has already been done in the past to get ideas. A number of frequency standards used xtal filter/buffers on the output of their oscillators, like this HP schematic shown. The manuals quite often has a section on theory of operation that might be useful.
--- End quote ---
Thank you!
Here on my instagram I have a picture of the output stage without and with the filter.
https://www.instagram.com/metslab/
The harmonic content of the output has bigger even harmonics, I think because the class A emitter folower of the output stage. Anyway, I think it`s working fine.
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