Simple Symetrical Amplifier

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#4,103
I sim BIGBT with emitter follower and have better THD and slew rate than 3EF (with my own IPS). Is NPN and PNP at source and drain of mosfet essential to be matching? Can you suggest how to stabilize the bias current?
 

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#4,104
Of course it is better in overall than 3EF, easy job for Q1, 2 as predrivers.

V3 should have exactly inverted voltage/temp curve as an uncompensated output stage on the main heatsink, excludind predrivers Q1, 2. Try to simm uncompensated output stage in operating temperature range and observe output bias according to V3. Inverted curve for V3 means proper compensation, keeping the bias constant (in theory).

V3 can be realised as discrete BJT temp sensor compensated Vbe multiplier or as NTC compensated IC shunt regulator.

All PNP outputs should be matched to each other only, the same with NPN, as they have to share the output current in equal proportion.
 
#4,109
vzaichenko said:
Looks excellent to me. I will also experiment with simulation of this...
LC - thank you for pointing at it 😉
Click to expand...
If lateral mosfets are used as drivers temp compensation would be very easy, simple Vbe multiplier as temp sensor.

What is so special about BIGBT output stage:
- for six outputs per rail only three base currents flow through mosfet driver
- NPN-PNP base and therefore collector currents are completely equal
- very stable design no base-collector compensation capacitors needed
- very fast response especially if predrivers are used
- very easy to drive because of mosfet drive current isolation
- enormous output current capability

One good CFA should be proposed with this output stage. :up:
 
#4,113
I sim VBE multiplier with lateral mosfet (2SK1058/2SJ162).
Lateral mosfet on separate heat sink and I assume the temperature is 60 degree Celsius. pre-driver and final transistor on same heat sink with VBE multiplier.

If pre-driver on separate heat sink, it slightly over compensated.
If all mount on same heat sink, it slightly under compensated.
 

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#4,114
Laterals should be on the main heatsink in the middle of outputs. Pre-driver on separate heatsink on PCB. Slightly over compensated tempco is OK for safety reasons, in practice this can be just right. :yes:

Now one should bring to life this monster from :darkside: 😀
 
#4,116
Which one to use very much depends on implementation. Until now I've only used IRF610/9610 mosfets in BIGBT outputs, always without any issue. Lateral mosfets would certainly have some advantages like complete absence of secondary breakdown in SOA, negative tempco, low Ugs threshold voltage, no high frequency cross conduction, very robust and immune to oscillations. Sounds like I'm some kind of marketing manager but since I tested them a lot, there's practically no problems with them.

This case would be the first time to use lateral mosfets in BIGBT and I would definitely choose ALF08N20V and ALF08P20V. 🙂
 
#4,120
Lazy Cat said:
Which one to use very much depends on implementation. Until now I've only used IRF610/9610 mosfets in BIGBT outputs, always without any issue. Lateral mosfets would certainly have some advantages like complete absence of secondary breakdown in SOA, negative tempco, low Ugs threshold voltage, no high frequency cross conduction, very robust and immune to oscillations. Sounds like I'm some kind of marketing manager but since I tested them a lot, there's practically no problems with them.

This case would be the first time to use lateral mosfets in BIGBT and I would definitely choose ALF08N20V and ALF08P20V. 🙂
Click to expand...

thanks to your andwer

I already have hitachi but what most with the ALF?

This driver must be matched ?
 
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