All Hitachi Lateral Fet amplifier for DIY described by Paul Kemble

[Zen Mod]

if nothing else , using those mosfets for T8 and T9 CCS-es is waste

simple Wilson two bjt CCS for T8 position , mirrored to T9 position, is better solution , freq. wise and dyn. imp. wise

[donpetru]

Originally Posted by AndrewT

I would throw away T7 & T8 & T9 and go back to a BJT CCS and a BJT mirror.

Originally Posted by Zen Mod

if nothing else , using those mosfets for T8 and T9 CCS-es is waste

simple Wilson two bjt CCS for T8 position , mirrored to T9 position, is better solution , freq. wise and dyn. imp. wise

I'm not saying your recommendations are not good but not targeting recommendations to this topic, to create an audio amplifier with only MOSFET and/or JFET transistors.

Speaking of the latest version of CCS, not bad to be taken into account next CSS topology. Look at the attached image below.

[Zen Mod]

Originally Posted by donpetru

I'm not saying your recommendations are not good but not targeting recommendations to this topic, to create an audio amplifier with only MOSFET and/or JFET transistors.
........

your choice ;that's the same as you said that you want to make entire car wheel from steel

use whatever part , but best for position/role

Originally Posted by donpetru

......

Speaking of the latest version of CCS, not bad to be taken into account next CSS topology. Look at the attached image below.

which one - left (cascoded Jfet , depletion mode biasing ) , or right one (bjt+mosfet,enhanced mode biasing) ?

[donpetru]

Originally Posted by Zen Mod

your choice ;that's the same as you said that you want to make entire car wheel from steel

use whatever part , but best for position/role

Your comparison above is totally wrong.
This project it's just a theoretical exercise that would follow a practical approach. Must demonstrate that it can. What will get, remains to be seen.

Originally Posted by Zen Mod

which one - left (cascoded Jfet , depletion mode biasing ) , or right one (bjt+mosfet,enhanced mode biasing) ?

I mean of both CSS, from the right and left image posted above. Is just one example.

[gaborbela]

Hello

Actually I want to build these amplifier from all fet. Otherwise it will be just another amplifier....
After I test it we can always change to get better performance in case it will be a need.
Yes I want a good (or great) performance IT WOULD no reason to DIY!
For that reason I do not reject any idea specially when a few guys advise the same think!

Zen Mod
These how you tought to use BJT for T8 & T9?
Please let me know.
Thank you

Greetings Gabor

[AndrewT]

The amplifier can be all fet.
The CCSs are just sources and sinks for the current flows to/from the rails. they can be BJT and the amp is still all fet. At least that's my view.

If you don't afree then use jFETs wired as CCSs. You can add fet cascodes around the jfet CCSs, if you need more voltage capability.

[wahab]

Originally Posted by gaborbela

Hello

Actually I want to build these amplifier from all fet. Otherwise it will be just another amplifier....
After I test it we can always change to get better performance in case it will be a need.
Yes I want a good (or great) performance IT WOULD no reason to DIY!
For that reason I do not reject any idea specially when a few guys advise the same think!

Zen Mod
These how you tought to use BJT for T8 & T9?
Please let me know.
Thank you

Greetings Gabor

The collector and the emitter should be inverted in your schematic.
Also , using bipolar would allow to reduce the zener to a few volts ,
extending the maximum voltage swing , although it s doable
with mosfet current source , just take a 5.1V zener and set R3 to 470R ,
while R2 is to be changed to 1.5K.

The original value of 1.8K along with a 15V zener was indeed
not the good set in respect of the original schematic wich
used a 16K resistor to set the input stage current at about 4mA ,
while the combination Z15V/1K8 would have provided 8mA or so.


Anyway , once you have made the choices of components
i will do a few sims to check grossly how this work.

[gaborbela]

Originally Posted by wahab

The collector and the emitter should be inverted in your schematic.
Also , using bipolar would allow to reduce the zener to a few volts ,
extending the maximum voltage swing , although it s doable
with mosfet current source , just take a 5.1V zener and set R3 to 470R ,
while R2 is to be changed to 1.5K.

The original value of 1.8K along with a 15V zener was indeed
not the good set in respect of the original schematic wich
used a 16K resistor to set the input stage current at about 4mA ,
while the combination Z15V/1K8 would have provided 8mA or so.


Anyway , once you have made the choices of components
i will do a few sims to check grossly how this work.

Hello wahab
Thank you very much, sim would be great it would save a lot of energy and time. Eaching PC board, soldering etc.
I made those mode you ask for change those parts values, I hope now those BJT-s are OK.
(Usually collector connected to the supp voltage that is why I made that way.)
In case still no good I will re do it again.
Since I don't know those BJT-s drawn correct or not.
Any way I will stick with these Toshiba 2SC3423 transistor we already chose for cascode to.
Thanks one more time!

Greetings Gabor

[donpetru]

In the last diagram posted above, increase the value of R3 to 1K or decrease the value of Rt.

[wahab]

Originally Posted by gaborbela

Hello wahab
Thank you very much, sim would be great it would save a lot of energy and time. Eaching PC board, soldering etc.
I made those mode you ask for change those parts values, I hope now those BJT-s are OK.
(Usually collector connected to the supp voltage that is why I made that way.)
In case still no good I will re do it again.
Since I don't know those BJT-s drawn correct or not.
Any way I will stick with these Toshiba 2SC3423 transistor we already chose for cascode to.
Thanks one more time!

Greetings Gabor

Here a schematic that will summarize the lasts changes.
Some resistors are brought to the closer E12 values ,
such as 1.6K being changed to 1.5K in the input differential
current source collector.

Also , the gain is increased to 33 as the original value , 22 , is too low
for the expected output voltage , it is even likely that it must be
increased even more but it ca be changed later by swapping
the usual resistor.

A diode + led are connected in parralel with the biaising trimmer ,
as this will limit the current if ever the trimmer goes broken
or if it is too much rudly handled , in both case the led will
be bright only with faulty conditions.

The two compensation capacitors are increased to 47pF
to prevent oscillations , they can be later experimentaly reduced
to a lower value.