user 37518
Well-known member
;D
And that allows increasing seriously these base resistors, probably tenfold for a similar output swing. It would also reduce the idle current in the output pair.gyraf said:If you insist on running off 9V, I'd suggest that you bootstrap the output transistor driving.
That way you don't have to loose the two diode drops and the two B-E drops. Those 2.4V can make a big difference for the power available in this circuit..
Jakob E.
gyraf said:If you insist on running off 9V, I'd suggest that you bootstrap the output transistor driving.
That way you don't have to loose the two diode drops and the two B-E drops. Those 2.4V can make a big difference for the power available in this circuit..
Jakob E.
PRR said:BTW: the old-old LM386 (get JRC) will do as well or better on 9V and 16r-up. You need two, but the total pincount is less than an 8DIP and two Qs. THD is not stellar but may be no worse than a 358 and basic buffer. Wire the '386 for low gain (20) so its hiss is not bad. Do not forget the RC load on the output to suppress MHz squirreliness.
user 37518 said:How would you bootstrap this circuit? I imagine something like splitting the 470 ohm resistors in half and adding a capacitor from the output to the the joint between the 2 resistors?
Actually this is a common topology for not very hifi applications using modern (fast) op amps. The common collector NPN and PNP output buffer devices, with the bases tied together still exhibit a normal Vbe drop because the other complementary base-emitter junction in parallel is reverse biased and not conducting half the time. Adding a modest resistor from base to emitter, allows the op amp to supply some current during the crossover region between -0.5V and +0.5V. For outputs greater than +/-0.5V the buffer transistors conduct and supply current as expected.ruffrecords said:Forgive my ignorance but do you mean tie the two bases together? Even then you must lose the Vbe surely or is there something smart going on?
Cheers
Ian
The resulting performance was deemed adequate by the Studer engineers, who had a reputation of never sacrificing performance to petty savings.JohnRoberts said:Actually this is a common topology for not very hifi applications using modern (fast) op amps.
The old 301, with the feedforward compensation, was relatively fast for back in its day... (I wonder if the current feedback into the + input, bothers the FF compensation that only works with inverting topology? Probably not much voltage swing there from current into the 6.8r .)abbey road d enfer said:The resulting performance was deemed adequate by the Studer engineers, who had a reputation of never sacrificing performance to petty savings.
They used it in conjunction with positive current FB in order to minimize transformer distortion.
To deliver current to the output before the transistors are turned on.user 37518 said:Whats the purpose of the resistor (R34) between the base and emmiters in the Studer schematic?
Enter your email address to join: