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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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