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Current Dumping Amplifier by G. Schmidt

HiFi, LoFi, Tubes, Transistors, ICs, Commercial, DIY

Current Dumping Amplifier by G. Schmidt

Postby Ravindra » Thu Sep 18, 2014 4:40 pm

Hello,

I am starting a thread on current dumping Amplifier by G. Schmidt.

I have the Indian edition of 301 circuits. The current dumping amplifier by G Schmidt is of interest to me and I am planning to make it.
The design is several years old. I am wondering if I can change some of the components with better ones.
I feel that there is also some scope to improve some features of it. Kindly let me know your thoughts.

With reference to the circuit in the attachment:

1. If anyone has built this, can they comment on their experience: stability, sound, heat dissipation compared to Class-AB.
2. The published design uses 741, a general purpose op-amp. Will a better op-amp like LME49710 that have very low noise and high slew rate?
3. The transistors T1 & T4 in the supply rails are biased by resistor divider. This will need a stabilized amplifier supply. Will it be better to regulate the bias using a zeners in place of R3 and R6 and re-calculating R3 and R5 as required?
4. The drivers T2 and T5 (BD139 and BD140) are driven from the collectors of T1 and T4. Will it be better if they are driven by a current mirror inserted between R4-T1 and R7-T4?

I know that the design and the topology is old. But having a class-b output with no crossover distortion, no bias settings and no thermal issues is the type of topology that excites me. Hopefully the power dissipation will also be better than a typical Class-AB amplifier

I look forward to some interaction on this.

Regards,

Ravindra.
Attachments
Current Dumping Amplifier.GIF
Last edited by Ravindra on Fri Sep 19, 2014 6:38 am, edited 1 time in total.
Ravindra
 
Posts: 6
Joined: Thu Sep 18, 2014 3:21 pm

Re: Current Dumping Amplifier by G. Schmidt

Postby Ravindra » Fri Sep 19, 2014 3:25 am

Upon some thought, it seems to me that 3. in my list above should be ok.
However, not 4. This is because the the purpose is not to mirror the op-amp rail current into the drivers but to let the drivers be in Class-B till about 50% of the op-amps current capability and at that point let the drivers drive the output transistors take over.

Regards,

Ravindra.
Ravindra
 
Posts: 6
Joined: Thu Sep 18, 2014 3:21 pm


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