good morning I apologize if I insert myself brutally... The simulations did not show these distortions...
That's a CFP with gain, tends to underperform quite a bit compared to CFP follower, as the feedback is too heavily loaded - you either have poor THD or R4/R5 have to dissipate a lot more power than you would like to linearize the feedback path (i.e. swamp the non-linear current demand of TR1). If you make R4 << R5 you have only a small bit of gain, but this can be handy for getting the most out of the supply rails, and its more linear as its almost a follower.Sorry to go off topic This is a 2 bjts circuit Very classic but it seems that almost nobody consider it Why ?
https://www.electronics-notes.com/images/transistor-two-device-amplifier-circuit-01.svg
when optimized it should have low THD and low Zout I do not about its PSRR
i wonder if it could be done with same 2 npn
Hi i have tried the schematic but using resistors and the THD spectrum at 1kHz at least looks quite nice (i wonder about its limits)View attachment 1307161
I built this up in sim early in the thread but it didn't fit the criteria and then discussion shifted to the 317 circuit, and I never posted it. Using Barry Blesser's "Super Transistor" (h/t Scott Wurcer) and @MarcelvdG's idea of CRDs, I tried to stay within the bounds of the original criteria as much as possible. I think this would require one trace cut in the original circuit, at the original base. The top side (schematic-wise) of the cut would connect to the collector-base junction, the bottom side to the input emitter. I never saw details on the source and load impedances. I used 9.56k from original schematic as load R, and tested with 50, 1k, and 10k source impedances. I did not breadboard as I have no CRDs.
I used the Central Semi CRDs because their Spice models were easy to access. The CCL0130 models give 90uA rather than the expected 130uA. After checking the datasheet, 90uA looks about right for 27C, with 130uA at a higher temp (high, positive tempco--may require a different R5 value, a parallel resistor, or be unusable in real world application). Qspice sim attached, models embedded. For other programs, Central Semi CRD model file attached (CCL.txt), and BJTs are the Cordell models.
Sim results (when three values given, read as RS=50/1k/10k):
-Input impedance (ohms): 116K with variance <1k across frequency.
-Gain(dB) @ 1k: -0.005/-0.08/-.72
-Frequency Response: <-.04dB at 20hz
-Input referred noise @ 1kHz (nV/rtHz): 2.8/6.3/34.8
-Input referred noise @ 20Hz (nV/rtHz): 8.1/9.9/35.6
-SNR ref 1Vrms (dB): 128/122/108
-THD1k 1Vrms (dB): -119/-111/-96
-THD1k 5Vrms (dB): -78/-68/-52
-THD20k 1Vrms (dB): -102/-92/-76
-THD20k 5Vrms (dB): -78/-67/-51
FR can be flattened by increasing output C. LF Noise rise can be reduced by increasing input C. 47u for both caps gets rid of both issues.
THD is primarily 2H. Lowest load resistance that does not clip with 7.071Vpk input is 1.5k.
Input impedance is parallel of R5 and the super-transistor's "base" at emitter Q1. At LF, the impedance looking into Q1 emitter is approximately Beta(Q2)*RL, but at megaohms like you get with 10k load, it's less (presumably early effect and output impedance of current source).
Hi it's me again I did as you recommended i.e. using the cfp as a buffer and ended with a very clean 1kHz THD spectrumThat's a CFP with gain, tends to underperform quite a bit compared to CFP follower, as the feedback is too heavily loaded - you either have poor THD or R4/R5 have to dissipate a lot more power than you would like to linearize the feedback path (i.e. swamp the non-linear current demand of TR1). If you make R4 << R5 you have only a small bit of gain, but this can be handy for getting the most out of the supply rails, and its more linear as its almost a follower.
Hi please excuse me if i disturb you But i have open the Cordell models list and found very interesting models that i would like to add to the default library of LTSpiceView attachment 1307161
I built this up in sim early in the thread but it didn't fit the criteria and then discussion shifted to the 317 circuit, and I never posted it. Using Barry Blesser's "Super Transistor" (h/t Scott Wurcer) and @MarcelvdG's idea of CRDs, I tried to stay within the bounds of the original criteria as much as possible. I think this would require one trace cut in the original circuit, at the original base. The top side (schematic-wise) of the cut would connect to the collector-base junction, the bottom side to the input emitter. I never saw details on the source and load impedances. I used 9.56k from original schematic as load R, and tested with 50, 1k, and 10k source impedances. I did not breadboard as I have no CRDs.
I used the Central Semi CRDs because their Spice models were easy to access. The CCL0130 models give 90uA rather than the expected 130uA. After checking the datasheet, 90uA looks about right for 27C, with 130uA at a higher temp (high, positive tempco--may require a different R5 value, a parallel resistor, or be unusable in real world application). Qspice sim attached, models embedded. For other programs, Central Semi CRD model file attached (CCL.txt), and BJTs are the Cordell models.
Sim results (when three values given, read as RS=50/1k/10k):
-Input impedance (ohms): 116K with variance <1k across frequency.
-Gain(dB) @ 1k: -0.005/-0.08/-.72
-Frequency Response: <-.04dB at 20hz
-Input referred noise @ 1kHz (nV/rtHz): 2.8/6.3/34.8
-Input referred noise @ 20Hz (nV/rtHz): 8.1/9.9/35.6
-SNR ref 1Vrms (dB): 128/122/108
-THD1k 1Vrms (dB): -119/-111/-96
-THD1k 5Vrms (dB): -78/-68/-52
-THD20k 1Vrms (dB): -102/-92/-76
-THD20k 5Vrms (dB): -78/-67/-51
FR can be flattened by increasing output C. LF Noise rise can be reduced by increasing input C. 47u for both caps gets rid of both issues.
THD is primarily 2H. Lowest load resistance that does not clip with 7.071Vpk input is 1.5k.
Input impedance is parallel of R5 and the super-transistor's "base" at emitter Q1. At LF, the impedance looking into Q1 emitter is approximately Beta(Q2)*RL, but at megaohms like you get with 10k load, it's less (presumably early effect and output impedance of current source).