TSSA - The Simplest Symmetrical Amplifier

[Idefixes]

Originally Posted by Lazy Cat

Mostly any 5 mm IR LED is okay.

At current If=3,5 mA, forward IR LED voltage is app. 1,2 V and that is too low for proper cascode, so please provide two of them in series on the PCB. That will provide Vce=1,8V for VAS BC transistor.

Ok i will do the modification.

Marc

[MiiB]

what is the benefit from the BIGBT...??

[Lazy Cat]

Originally Posted by MiiB

what is the benefit from the BIGBT...??

Hi MiiB

Mhmm I simply love this BIGBT

Easy to drive (low input gate capacitance) output transistor (yes I consider BIGBT as one joint part only), very stabile output transistor as integrity (balanced conditions for NPN/PNP), IRF conduct only one base current for both outputs, so for one base current (and it is the same for both outputs) through IRF driver you get two parallel collector curents for the output (doubled hFE). Linear transconductance dIout/dVg, high speed ... you should try it once.

[Lazy Cat]

Update released

Changes:

- VAS cascode - two IR LED per cascode
- "ON" RED LED added - indicates bias-on state

Regards Andrej

[terranigma]

Originally Posted by AndrewT

the simplest !

post71 shows ~75 components.

I couldn't even count it.

[MiiB]

What happens when R6 and R7...are modulated with the input signal...??

[Lazy Cat]

R6, R7 are voltage dumpers to CCS, necessary to use because 2N j-fets have too low Vds/power dissipation specs. Current through R6, R7 is constant as CCS-s are capable of, so ideally no modulation should be present on these resistors. Of course it would be better to use source/sink transistors without voltage dumpers (double cascoded CCS). CCS are not ideal and there's always tendency to have increasing level of distortions according to higher frequencies. Separate measurements of CCS shows their capability to maintain the current to be constant. If you suggest to replace the resistors with improved CCS-s you are invited to do so.

Possible ripple suppression would be to add small parallel caps across R6, R7, just to prevent AC modulation (low level ripple) as voltage drop on them.

[Lazy Cat]

Originally Posted by terranigma

I couldn't even count it.

Question

Originally Posted by Bigun

jeez, this is supposed to be the Simplest ? I think this thread has lost the plot along the way. Pitty, I like really simple.

Answer

Originally Posted by Lazy Cat

Hi Bigun

I can not manage more than two threads simultaneously, so logically one would be full of stuff.

From simple to more complex version, all based on the same TSSA base core. It is the same like in school, gradually progressing the knowledge.

Regards Andrej

I hope you find it reasonable.

[MiiB]

what if you reverse the positions.. so you place the resistors at the rails and the current sources where they belong. then you get both....reduced dissipation and no signal induced current modulation.

[MiiB]

Think you should rearrange the driven VAS cascode... make the connection inside the Rail resistors for the input pair.