Charles Steinmetz writes: >> The diode-connected 2N3904 has less leakage at a small forward >> voltage than any small-signal diodes I tested > > Generally, one uses the B-C junction rather than the B-E junction for > this, because (i) being a smaller junction (in most small-signal > BJTs), it has less leakage than the B-E junction,
The smaller junction in a discrete BJT is always the emitter. The breakdown and reverse leakage characteristics are different due to the different doping profiles. > and (ii) it has a much higher reverse breakdown voltage than the ~5v > breakdown of the B-E junction (NB: the B-E junction is degraded with > even very brief operation in the breakdown region). I think the circuit depends on the forward characteristics of the diode from the brief look I've had. In this case, a diode connected npn as shown (shorting the base and collector) produces a much better diode characteristic than any "true" diode would. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ Factory and User Sound Singles for Waldorf Q+, Q and microQ: http://Synth.Stromeko.net/Downloads.html#WaldorfSounds _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.