Differences between various vbe multipliers

[kees52]

I have made a temp plot, however I do not now if LTspice does include all parts, I need to rule out some.

 

[kees52]

This one is final, it do work fine keeping idle current into the 50 mA range between 20 and 80 degree oC Can go make the pcb for the circlotron now.

I have use a extra bjt Q3 for the regulator transistor Q2 because these did change with temperature, now it is rock solid, tested with soldering iron against it to get it hot. I did connect these two transistors thermally, reason is the multiplier and special Q2 do draw 60 mA.

regards

 

[tiefbassuebertr]

In order to get as complete an overview as possible of what approaches there are to Vbe multipliers, I have compiled the existing threads from here to this topic:
https://www.diyaudio.com/community/threads/optimizing-the-vbe-multiplier.216385/
https://www.diyaudio.com/community/threads/vbe-bias-generator-insights.362815/#post-6406955
https://www.diyaudio.com/community/threads/diodes-and-vbe-multipliers.385184/page-2
https://www.diyaudio.com/community/threads/vbe-multiplier-current-compensation-resistor.365670/
https://www.diyaudio.com/community/threads/on-vbe-multipliers.301086/
https://www.diyaudio.com/community/...istoric-vbe-multiplier-biasing-system.284379/
https://www.diyaudio.com/community/threads/doug-self-editing-errors.106137/ (post #2)
https://www.diyaudio.com/community/threads/stv-4h-and-stv-3h-diodes-array.83778/page-2
https://www.diyaudio.com/community/threads/nfb-with-vbe-multiplier-better-than-cfp.376347/
https://www.diyaudio.com/community/threads/vbe-multiplier.143137/
https://www.diyaudio.com/community/...eedback-using-floating-vbe-multiplier.376276/
https://www.diyaudio.com/community/threads/vbe-multiplier-sensitivity.15457/
https://www.diyaudio.com/community/threads/why-bd139-vbe-multiplier.215732/
https://www.diyaudio.com/community/threads/thermal-compensation-of-vbe-multiplier.107427/
https://www.diyaudio.com/community/threads/problems-with-vbe-multiplier.239893/

https://www.diyaudio.com/community/threads/mixing-thermaltrak-with-non-thermaltrak.336761/
https://www.diyaudio.com/community/threads/sanken-output-transistors-std03n-p-new.148456/
https://www.diyaudio.com/community/threads/thermaltrak-transistors-have-been-discontinued.237929/
https://www.diyaudio.com/community/...odels-with-sankens-sap-std-series-why.317340/
https://linearaudio.net/sites/linearaudio.net/files/v9 jd.pdf
https://www.diyaudio.com/community/threads/thermaltrack-from-on-semi.310195/
https://www.diyaudio.com/community/threads/on-semi-thermaltrak.71534/
https://www.diyaudio.com/community/threads/techno-sap130-std03p-std03n-130-watt-hifi.276451/

 

[tiefbassuebertr]

For more easy finding previous post in a better overview -
BIAS approaches for Idle Current Stabilizing in Class AB Output Buffer Stages of Power Amplifiers (independent of ambient Temperature, with BjT's only)

1) Vbe multiplier (Transistor) vs. diode(s) only
https://www.diyaudio.com/community/threads/diodes-and-vbe-multipliers.385184/
https://www.diyaudio.com/community/threads/stv-4h-and-stv-3h-diodes-array.83778

Differences between Diodes and Transistor(s) on BIAS circuits as follow:
a. two diode vs. Vbe multiplier: single Transistor - Darlington - Darlington+Rcomp (Hagerman)
http://www.hagtech.com/pdf/vbe.pdf
https://www.diyaudio.com/community/threads/hagermans-vbe-multiplier.2266/
https://www.diyaudio.com/community/threads/vbe-bias-generator-insights.362815/
b. diodes only vs. Vbe multiplier+Rcomp: single transistor vs. push-pull (Hawksford)
https://www.diyaudio.com/forums/att...ified-diode-bias-circuit-audio-amplifiers-pdf
c. push-pull Vbe multiplier + non switching class-B push-pull CFP output power buffer
https://www-f9.ijs.si/~margan/Articles/Class_B_Dist.pdf
d. Darlington Vbe Multiplier in real live
http://hifisonix.com/wordpress/wp-content/uploads/2020/02/The-Ovation-nx-Amplifier-V2.10.pdf
e. Sziklai-Darlington (CFP) Vbe Multiplier - post #6 under
https://www.diyaudio.com/community/...istoric-vbe-multiplier-biasing-system.284379/
f. Bias with 3V9 zener + AC bypass
https://www.diyaudio.com/community/threads/beefing-up-an-nva-ap10p-amp.212450/#post3026619

2) calculating Rcomp in Vbe multiplier circuits
https://electronics.stackexchange.c...emitter-resistance-cancellation/449975#449975
https://www.diyaudio.com/community/threads/vbe-multiplier-current-compensation-resistor.365670

3) best Vbe transistor
https://www.diyaudio.com/community/threads/optimizing-the-vbe-multiplier.216385/page-3 (post #41)
https://www.diyaudio.com/community/threads/why-bd139-vbe-multiplier.215732/
https://www.diyaudio.com/community/threads/on-vbe-multipliers.301086/

4) Vbe multiplier from Mark Levinson/Madrigal (adaptive bias)
https://www.diyaudio.com/community/threads/optimizing-the-vbe-multiplier.216385/page-3 (post #56)
http://www.audiodesignguide.com/doc/adapbias.htm
https://www.diyaudio.com/community/...automatic-self-biased-overview-wanted.164939/
https://www.diyaudio.com/community/threads/adaptive-bias-theory.88309/
https://www.diyaudio.com/community/threads/simple-adaptive-bias-bipolar-amp.331304/
https://www.diyaudio.com/community/threads/adaptive-class-a.98325/

5) Temperature Compensation and thermal dynamics in Class-B PP power follower
a. External
https://hifisonix.com/audio-amplifier-temperature-compensation/
https://www.diyaudio.com/community/...r-resistor-for-thermal-bias-stability.178160/
https://www.diyaudio.com/community/threads/thermal-compensation-of-vbe-multiplier.107427/
http://www.renardson-audio.com/B-amp.html
https://www.diyaudio.com/community/threads/vbe-thermal-coupling-issue.48971/
https://www.diyaudio.com/community/threads/doug-self-editing-errors.106137/
Thermal Dynamics page 505 book title: "Audio Power Amplifier Design" (D. Self)
https://www.diyaudio.com/community/threads/vbe-multiplier-sensitivity.15457/ (BD135-137-139, MJE340 and BS170 as Vbe multipl.)
https://www.diyaudio.com/community/threads/thermal-compensation-of-vbe-multiplier.107427/ (thermal reaction - post #9)
b. Internal (SANKEN Thermaltrak Series)
https://www.diyaudio.com/community/threads/mixing-thermaltrak-with-non-thermaltrak.336761/
https://www.diyaudio.com/community/threads/sanken-output-transistors-std03n-p-new.148456/
https://www.diyaudio.com/community/threads/thermaltrak-transistors-have-been-discontinued.237929/
https://www.diyaudio.com/community/...odels-with-sankens-sap-std-series-why.317340/
https://linearaudio.net/sites/linearaudio.net/files/v9 jd.pdf
https://www.diyaudio.com/community/threads/thermaltrack-from-on-semi.310195/
https://www.diyaudio.com/community/threads/on-semi-thermaltrak.71534/
https://www.diyaudio.com/community/threads/techno-sap130-std03p-std03n-130-watt-hifi.276451/

6) Floating Vbe Multiplier
https://www.diyaudio.com/community/...eedback-using-floating-vbe-multiplier.376276/

7) Unusual Approach
https://www.diyaudio.com/community/threads/nfb-with-vbe-multiplier-better-than-cfp.376347/
https://hifisonix.com/hifisonix-kx-amplifier-v2/
https://www.diyaudio.com/community/threads/new-hifisonix-kx2-amplifier.374028/

8) Replacing Vbe Multiplier by Auto-Bias (Bias-Servo)
https://www.diyaudio.com/community/...istoric-vbe-multiplier-biasing-system.284379/

9) Individual Issue
https://www.diyaudio.com/community/threads/problems-with-vbe-multiplier.239893/

 

[tiefbassuebertr]

in post #25 under
https://www.diyaudio.com/community/threads/diodes-and-vbe-multipliers.385184/page-2#post-7001033
I have found an interesting observation concerning thermal runaway.

 

[tiefbassuebertr]

The version of fig. 2d under
http://www.hagtech.com/pdf/vbe.pdf
I have found in the Harman HK610 - go to second attachment in post #22 under
https://www.diyaudio.com/community/threads/stk0039-discrete-component-replacement.348391/page-2