Electronics > Projects, Designs, and Technical Stuff
Power Amplifier AB class
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strawberry:
Amplifier board for amplifier repair and mod
Output power: 100W
THD+N: unknown
Slewrate: 18VuS
Bandwith: 15Hz..150kHz
Power supply: +/-10..50V
Amplifier topology: Voltage amplifier
Amplifier class: AB
Parts list: 2SA1943N,  2SC5200N,  TTA004B, TTC004B, KSA992,  KSC1845, BSS169, SSM3K15F, wima film capacitors,  1206 size chip resistors/ceramic capacitors, Piher trimmer, 0.22R low inductance KOA Speer resistors, 
mariush:
Looks interesting but I wonder if it's really worth it when you can buy AB class amplifier chips like TDA7294 (link to datasheet and example circuit)

unless your circuit has very low thd, seems like 6$ per chip would be reasonable, when i can save pcb space and reduce component count.
plus i don't have to hunt potentially rare transistors or have to match them...
strawberry:
Old amplifiers with STK modules... Power supply voltage is near 50V or above, wont leave any margine for TDA7294 LM3886.. 40V (recomended max)
Osciloscope and FFT give promising resaults up to 50kHz
mariush:
It's +/- 40v ... split power supply.... so up to 80v ... you can easily use 48v AC transformers with center tap or two 24v secondary windings.

And you can wire two modules in bridge mode and power them basically from up to 80v ... see datasheet, page 13
David Hess:

--- Quote from: mariush on May 13, 2019, 08:59:45 am ---Looks interesting but I wonder if it's really worth it when you can buy AB class amplifier chips like TDA7294 (link to datasheet and example circuit)

unless your circuit has very low thd, seems like 6$ per chip would be reasonable, when i can save pcb space and reduce component count.
--- End quote ---

The integrated or hybrid solution has a lot of advantages including ease of use, size, and cost.  But a discrete solution can be higher performance and will be better about handing heat dissipation.

To just give one example, both of these designs use emitter degeneration to increase full power bandwidth which is common in audio power amplifiers however this raises the input noise by enough that it will be audible in the speaker.  A discrete design, although not this one, could avoid this to make a "noiseless" power amplifier.


--- Quote ---plus i don't have to hunt potentially rare transistors or have to match them...
--- End quote ---

The transistors are not rare (even now) and do not need to be matched in most discrete designs.
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