25 Watt Kinda Blameless with TMC, fast amplifier

lineup · 2024-03-09 7:31 am

thanks @catd @Hennady Kovalsky and @HAYK

I wiill look into the overshot with squarewave

lineup · 2024-03-09 7:50 am

I changed C2 from 22pF to 68pF.
Now the overshot should be gone.
Bandwidth is now like 1.5 MHz.

What can be done about the clipping behavior?

ZoltanChivay · 2024-03-09 8:03 am

catd said:
But there is also very bad clipping behavior in case of overload, e.g. with input sine 1.4 Vpp, see attached picture.
Seems the output went to constant voltage

What about this? This phenomenon seems extremely dangerous to me
Imagine a source with a high level and suddenly we get about -18V DC voltage at the amplifier output....
The speaker goes up in smoke....

catd - thanx for sharing .asc file

lineup · 2024-03-09 8:43 am

I added an anti clipping diode.
Now it is okay.

ZoltanChivay · 2024-03-09 8:44 am

C2=68pF Square wave 20kHz....

ZoltanChivay · 2024-03-09 8:51 am

With diode....

lineup · 2024-03-09 9:06 am

This is the Scope 20kHz squarewave.

ZoltanChivay · 2024-03-09 9:13 am

lineup said:
@ZoltanChivay
Your circuit is not correct.
Check the VAS transistors .....

?

catd · 2024-03-09 10:28 am

ZoltanChivay said:
C2=68pF Square wave 20kHz....

To compare this correctly with the @lineup-circuit, you should disable RI, CI. (Then it gets worse).
To reach the same result as with RI,CI, but only by increasing C2,
C2 must be min. 100p.
This then increases THD by an order of magnitude,
while THD is decreased when using RI,CI.

ZoltanChivay said:
What about this? This phenomenon seems extremely dangerous to me

I don't really know what's going on there. ?Seems @lineup hasn't simulated this?
Is it a "special feature" of LTSpice? can't imagine this....

@lineup
I've listed the models I used below so you can compare them with yours.
BJT models come from the LTwiki.
Mosfet models are from Ian Heglun and were posted a few days ago in another thread you may have seen. There are other models of the same mosfets in the same post mentioned, but for them LTSpice reports an error with curly brackets...

.model 2N3906 PNP(IS=1E-14 VAF=100 BF=200 IKF=0.4 XTB=1.5 BR=4 CJC=4.5E-12 CJE=10E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=NXP)

.model 2N3904 NPN(IS=1E-14 VAF=100 Bf=300 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=NXP)

.MODEL KSA1381 pnp IS=5.5544E-14 BF=148 BR=1.592 ISE=2.0546f NE=1.5 ISC=3.24807E-10 NC=2 VAF=580 VAR=100 IKF=0.2163 IKR=0.087544 RB=10.18 RE=0.0512 RC=4.072 CJE=9.572p VJE=0.748 MJE=0.371 FC=0.5 CJC=1.147p VJC=0.541 MJC=0.329 TF=1.0312E-09 XTB=0.907 EG=0.62 XTI=3

.MODEL KSC3503 NPN IS=2.0893E-14 BF=101.5 NF=1 BR=7.655 NR=1.007 ISE=4.3652E-14 NE=1.5 ISC=1.2598n NC=2 VAF=717.25 VAR=13.16 IKF=0.2512 IKR=0.0832 RB=2.98 RBM=0.001 IRB=0.001 RE=0.5305 RC=0.9 QCO=0.05 RCO=50.1187 VO=2.476 GAMMA=1.8231E-7 CJE=6.6039E-11 VJE=0.7017 MJE=0.3253 FC=0.5 CJC=6.6072p VJC=0.5 MJC=0.2439 XCJC=0.6488 XTB=1.4089 EG=1.2129 XTI=3 Vceo=300 Icrating=100m mfg=Fairchild

.model 10N20-75C VDMOS (Rg=60 Vto=0.09 Lambda=3m Rs=0.277 Kp=0.92 Rd=0.7 Ksubthres=0.11 Mtriode=0.3 Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p m=0.7 VJ=2.5 IS=4.0E-6 N=2.4 mfg=IH150521)

.model 10P20-75C VDMOS (pchan Rg=60 Vto=-0.45 Lambda=5m Rs=0.432 Kp=0.745 Rd=0.2 Ksubthres=0.14 Mtriode=0.4 Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p m=0.7 VJ=2.5 IS=4.0E-6 N=2.4 mfg=IH150521)

ZoltanChivay · 2024-03-09 10:45 am

catd said:
I don't really know what's going on there. ?Seems @lineup hasn't simulated this?
Is it a "special feature" of LTSpice? can't imagine this....

I did a lot of different simulations in LTspice I haven't seen a case like this before...Very strange

ZoltanChivay · 2024-03-09 10:53 am

lineup
can you simulated Vin=1,4pp in multisim?

lineup · 2024-03-09 11:12 am

catd said:
To compare this correctly with the @lineup-circuit, you should disable RI, CI. (Then it gets worse).
To reach the same result as with RI,CI, but only by increasing C2,
C2 must be min. 100p.
This then increases THD by an order of magnitude,
while THD is decreased when using RI,CI.

I don't really know what's going on there. ?Seems @lineup hasn't simulated this?
Is it a "special feature" of LTSpice? can't imagine this....

@lineup
I've listed the models I used below so you can compare them with yours.
BJT models come from the LTwiki.
Mosfet models are from Ian Heglun and were posted a few days ago in another thread you may have seen. There are other models of the same mosfets in the same post mentioned, but for them LTSpice reports an error with curly brackets...

.model 2N3906 PNP(IS=1E-14 VAF=100 BF=200 IKF=0.4 XTB=1.5 BR=4 CJC=4.5E-12 CJE=10E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=NXP)

.model 2N3904 NPN(IS=1E-14 VAF=100 Bf=300 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=NXP)

.MODEL KSA1381 pnp IS=5.5544E-14 BF=148 BR=1.592 ISE=2.0546f NE=1.5 ISC=3.24807E-10 NC=2 VAF=580 VAR=100 IKF=0.2163 IKR=0.087544 RB=10.18 RE=0.0512 RC=4.072 CJE=9.572p VJE=0.748 MJE=0.371 FC=0.5 CJC=1.147p VJC=0.541 MJC=0.329 TF=1.0312E-09 XTB=0.907 EG=0.62 XTI=3

.MODEL KSC3503 NPN IS=2.0893E-14 BF=101.5 NF=1 BR=7.655 NR=1.007 ISE=4.3652E-14 NE=1.5 ISC=1.2598n NC=2 VAF=717.25 VAR=13.16 IKF=0.2512 IKR=0.0832 RB=2.98 RBM=0.001 IRB=0.001 RE=0.5305 RC=0.9 QCO=0.05 RCO=50.1187 VO=2.476 GAMMA=1.8231E-7 CJE=6.6039E-11 VJE=0.7017 MJE=0.3253 FC=0.5 CJC=6.6072p VJC=0.5 MJC=0.2439 XCJC=0.6488 XTB=1.4089 EG=1.2129 XTI=3 Vceo=300 Icrating=100m mfg=Fairchild

.model 10N20-75C VDMOS (Rg=60 Vto=0.09 Lambda=3m Rs=0.277 Kp=0.92 Rd=0.7 Ksubthres=0.11 Mtriode=0.3 Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p m=0.7 VJ=2.5 IS=4.0E-6 N=2.4 mfg=IH150521)

.model 10P20-75C VDMOS (pchan Rg=60 Vto=-0.45 Lambda=5m Rs=0.432 Kp=0.745 Rd=0.2 Ksubthres=0.14 Mtriode=0.4 Cgdmax=100p Cgdmin=5p a=0.25 Cgs=600p Cjo=1100p m=0.7 VJ=2.5 IS=4.0E-6 N=2.4 mfg=IH150521)

I will try with C2=100pF
But my squarewave doesnt indicate a problem with 68pF

I will input those MOSFET models. Hope they work.

Does your simulation see if the anti clipping diode work?

lineup · 2024-03-09 11:22 am

MOSFET models do not work.
There is not somthing called VDMOS in Multisim.
I tried with NMOS but this did not work either.

Actually the squarewave is perfect with 47pF for C2.
How come you see a problem?

Hennady Kovalsky · 2024-03-09 11:43 am

lineup said:
I added an anti clipping diode.

where did you add it?
and why did they add it?
your U6 is “going crazy” from the signal, it needs a resistor in the collector and increase the current to him

Mark Tillotson · 2024-03-09 12:11 pm

Pretty clear to me this latchup is a simulation artifact of some sort... This topology works.

catd · 2024-03-09 12:45 pm

If I simply use a BD139 for U5, the LTSpice sim also works with increased Vin and clipping.
Then the “anti-clipping diode” D1 has an influence.
It actually seems to be a simulation error.

lineup · 2024-03-09 3:03 pm

Hennady Kovalsky said:
where did you add it?
and why did they add it?
your U6 is “going crazy” from the signal, it needs a resistor in the collector and increase the current to him

This is circuit I have to trust in. Because it simulates very well in my software.
Here you can see the anti clipping diode. It is also in @catd circuit.

lineup · 2024-03-09 3:38 pm

Code:

.MODEL ksc3503  NPN
+ IS=3.510E-14            BF=174.09             VAF=600
+ IKF=0.12325             ISE=2.2538E-13        NE=2.0
+ BR=0.64499              VAR=100               IKR=0.43102
+ ISC=6.4644E-10          NC=1.5                RE=0.048
+ RC=0.815                RB=8.134              RBM=0.034
+ IRB=3.0e-6              CJE=8.10E-12          MJE=0.401
+ VJE=0.75                CJC=8.20E-12          MJC=0.31
+ VJC=0.75                TF=9.995E-10          XTF=2
+ VTF=35                  ITF=1                 TR=1.0E-8
+ EG=0.84                 XTB=2.5               FC=0.5

ZoltanChivay · 2024-03-09 3:44 pm

My simulations (based on the .asc file added by catd) are still bad even with the values from the last post#37

I don't understand why. In the topic of the Cello amplifier, the results between LTspice and Multisim were very similar Where is the problem?

Hennady Kovalsky · 2024-03-09 6:19 pm

Название темы не соответствует необходимости установки дополнительных пассивных нелинейных элементов. Артефактное исследование)))).

lineup said:
This is circuit I have to trust in.

I see the topology of the circuit of the last century and I want to cry...

This design should have become single-stage long ago....

25 Watt Kinda Blameless with TMC, fast amplifier

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