); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] From: "Ulrich Bangert" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] ? phase comparison or other device Date: Fri, 29 Jun 2007 09:14:02 +0200 Message-ID: <[EMAIL PROTECTED]>
> Enrico, Ulrich, > you are right: Both of these articles should be read with Collins's > perhaps the better (and newer!) one. > > There is however one question remaining for me: When I learned > electronics it was generally considered bad design to let an amplifier > run into limiting due to supply limitations. If limiting was needed, so > was the rule, then it should be accomplished by planned feedback, say an > pair of antiparallel diodes in the feedback path. Can you give some > comments on whether this also applies to ZCDs or if really supply based > limiting is necessary? It is actually a specific design-trick on Collins behalf to saturate the op-amp since this infact acts like a noise-gate. By having the output stage saturated rather than operating linearly the noise as seen by the output RC filter is that of only the saturated transistor and not that of the input gained up. A diode limiter in the feedback path will maintain the op-amp in the linear operating range and thus cause the noise to continue to polute the output filter. What you can possibly acheive is the steer how deeply you run into output saturation tought. So, in this case op-amp saturation is a key trick to increased performance. Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
