Splitting the resistor in 2 and ac coupling the emitters together reduces the effects of Vbe and/or base biasing mismatch allowing a more symmetric output and/or operation at lower input signal levels.The inductor reduces the high frequency variations in the total emitter current. It also reduces the tail current noise at high frequencies. Bruce
On Sunday, 10 January 2016 10:05 AM, Attila Kinali <att...@kinali.ch> wrote: Moin John, Yes, I know I am comming back to an "old" discussion, but I have questions that need to be answered! :-) On Wed, 06 May 2015 08:56:10 -0400 John Ackermann N8UR <j...@febo.com> wrote: > Wenzel has published the schematic of an excellent squaring circuit. I > don't have the URL for their version handy, but I used it (with a couple > of mods) in the TADD-2 and TADD-2 Mini designs. You can see the > schematic in the T2-Mini users guide at > http://www.tapr.org/~n8ur/T2_Mini_Manual.pdf. The manual says: ---schnipp--- The purpose of the input circuit is to convert the RF input signal into a low-jitter square wave that can drive the PIC clock input. The circuit is closely based on the one published by Wenzel at http://www.wenzel.com/documents/waveform.html, with modifications suggested by Bruce Griffiths and Ulrich Bangert. The revised circuit works with inputs as low as -20dBm. ---schnapp--- The modification I can see is that the "current source" part of the differential pair changed from being a single, shared resistor of 100R to an inductor of 100uH, then splits up into two resistors of 220R, which are bridged by a 100nF capacitor. The inductor results in a reactance between 62R (100kHz) and 12k (20MHz) for the input range. Can you shed a bit of light on why you did those modifications and what the intended effect is? Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.