AndrewT said:
I know where you are going. This is not intended to run continuously at 2 x 400W/4ohm without forced cooling.
As the PGP http://www.synaesthesia.ca/Auxiliary-circuitry.html, this will have two fans, activated when air temperature into the case exceeds 60 degrees.
Quiescent power is about 80W/channel.
Re: Power Supply caps
1. DigiKey.
2. Yes, the doubled 4 is the V- pin reference.
3. Take a second look. That reference should have ideally zero tempco, it defines the Q107/Q120 bias, while the Q107/Q120 Vbe tempco is compensated by Q110/Q116 Vbe tempco. Two forward biased diodes won't, tempco speaking, do well.
PHEONIX said:
1. DigiKey.
2. Yes, the doubled 4 is the V- pin reference.
3. Take a second look. That reference should have ideally zero tempco, it defines the Q107/Q120 bias, while the Q107/Q120 Vbe tempco is compensated by Q110/Q116 Vbe tempco. Two forward biased diodes won't, tempco speaking, do well.
Re: Re: Power Supply caps
Are you talking about D110 , I was talking about U201 and U203
Why not have the heatsinks external an get rid of the fans and their associated noise.
Regards
AR
syn08 said:
Are you talking about D110 , I was talking about U201 and U203
Why not have the heatsinks external an get rid of the fans and their associated noise.
Regards
AR
I'm not going anywhere.syn08 said:
It was not a trick question.
I have a Pq=40W amp (2pair Re=0r1) on the stocks and I think it runs too warm (Ts~62degC).
I am considering Pq=56W (3pair Re=0r1).
I wanted to see what you were running yours at.
Re: Re: Re: Power Supply caps
Oh, sorry, yes.
1.5V is not enough for the cascode bias. You have to count one Q205/Q206 Vbe, plus the drop on R204/R215 (about 0.6V) leaving pretty much nothing for Q203/Q208 Vce. 2.5V is enough, but this would require no less than 4 forward biased junctions. It would work, but LM285 is a more compact solution, also having less DC current requirement and lower impedance.
PHEONIX said:
Oh, sorry, yes.
1.5V is not enough for the cascode bias. You have to count one Q205/Q206 Vbe, plus the drop on R204/R215 (about 0.6V) leaving pretty much nothing for Q203/Q208 Vce. 2.5V is enough, but this would require no less than 4 forward biased junctions. It would work, but LM285 is a more compact solution, also having less DC current requirement and lower impedance.
Re: Re: Re: Re: Power Supply caps
You say the above but can you tell me what the voltage across the LM285 is , I assumed it was 1.2 V and if it is then it does not follow the above statement. In the finished amp is the LM285 used or is it something else with higher voltage.
Regards
AR
syn08 said:
You say the above but can you tell me what the voltage across the LM285 is , I assumed it was 1.2 V and if it is then it does not follow the above statement. In the finished amp is the LM285 used or is it something else with higher voltage.
Regards
AR
Stuff
Hello Andy_C
Thanks for the link, so the LM285 is 2.5V and the LM385 is 1.2V is this correct.
Since you are the designer of the input trick of the CF output stage can you tell me if you need a bandgap reference to bias the input stage or can it be done with two diodes. My problem with the bandgap references is that they are noisey, but they win in their tempco performance.
Regards
AR
Hello Andy_C
Thanks for the link, so the LM285 is 2.5V and the LM385 is 1.2V is this correct.
Since you are the designer of the input trick of the CF output stage can you tell me if you need a bandgap reference to bias the input stage or can it be done with two diodes. My problem with the bandgap references is that they are noisey, but they win in their tempco performance.
Regards
AR
In my own application's output stage, I have a current gain of 7 from its input stage to its VAS, so I decided "better safe than sorry" and opted for the bandgap reference to get the best DC stability of the VAS current. I wouldn't want to speak for syn08 and his design though.
Noise in the output stage is far less of an issue than in the input stage, so I wouldn't worry about that.
Noise in the output stage is far less of an issue than in the input stage, so I wouldn't worry about that.
Re: Stuff
Yes. I have modified the schematics to clarify this, see the first post in this thread.
The bandgap references are decoupled, no need to worry about noise. Anyway, the LM385-1.2V noise is common mode.
PHEONIX said:
Yes. I have modified the schematics to clarify this, see the first post in this thread.
The bandgap references are decoupled, no need to worry about noise. Anyway, the LM385-1.2V noise is common mode.
I have a question about the 47 Ohm resistors in the Hawksford cascode (R204 and R215). Did these fix a parasitic oscillation or ringing?
andy_c said:
Yes. Without that, it trends to ring, in particular at high levels. 22ohm should be good enough, 47ohm is on the safe side.
Schematics of Yap 2.1
Hello Syn08
The Yap2.1 schematics you posted early in this thread are they working schematics of what you built, or did you build from other schematics which you have updated and not posted.
Regards
Arthur
Hello Syn08
The Yap2.1 schematics you posted early in this thread are they working schematics of what you built, or did you build from other schematics which you have updated and not posted.
Regards
Arthur
Re: Schematics of Yap 2.1
These are the schematics that I used to generate the netlist/ratsnet for the PCB layout, so they are exactly the current running topology. As of component values, you may want to do yourself a sanity check, although I'm 99.9% sure everything is fine.
BTW, this is the model for the 2.5V reference:
* Cathode
* Anode | |
* | |
.SUBCKT LM285 A K
Q1 3 2 1 0 NPN1 2.70
Q2 2 2 A 0 NPN1 1
R1 1 A 800 TC=0.00035
R2 4 2 2.4k
R3 4 3 7.2k
R4 5 4 3.28k
Q3 6 3 A 0 NPN1 1
R5 7 6 4k
Q4 10 5 7 0 NPN1 1
Q5 K K 5 0 NPN1 1
R6 2 12 1k
Q6 11 12 A 0 NPN1 0.2
Q9 K 11 13 0 NPN1 2
Q10 K 14 A 0 NPN1 10
R10 14 A 10k
R9 13 14 150
R7 K 8 800
Q7 10 10 8 0 PNP1 1
Q8 11 10 9 0 PNP1 1
D2 A K D1
D1 A 11 D3
R8 K 9 800
C1 K 11 20p
C2 6 3 20p
D3 11 K D2
*
*Adjust output voltage with Is
.MODEL NPN1 NPN(Is=0.8e-14 BF=100 VAF=100 TF=0.5e-9 RB=50 IKF=10m KF=1e-16 AF=1 RE=10)
.MODEL PNP1 PNP(Is=1e-14 BF=50 VAF=50 TF=1e-8 IKF=2m KF=1e-16 AF=1)
.MODEL D1 D(Is=1e-13 Rs=10 CJO=20p)
.MODEL D2 D(Is=1e-13 Rs=10 CJO=2p BV=5 IBV=10u)
.MODEL D3 D(Is=1e-13 Rs=10 CJO=2p )
.ENDS
And the macromodel for the 1.2V reference:
*-----------------------------------------------------------------------------
*
* connections: Anode
* | Cathode
* | |
.SUBCKT LM385 A K
*
* TWO-TERMINAL VOLTAGE REFERENCE
*
DFWD A K DF
GREV A K VALUE={LIMIT(20.00E-3*(EXP(V(A,K)/5.682E3)-1),-10M,0)}
RZ A 1 .102
GZ 2 1 VALUE={LIMIT(EXP(V(2,1)/198.0E-6),0,20.00E-3)}
EBV K 2 3 0 1
RBV 3 0 1.237E3 TC=1.139E-6 -346.8E-9
IBV 0 3 DC 1M
*
.MODEL DF D(IS=39.12E-15 RS=12.18 IKF=0 N=.9983 XTI=3)
.ENDS
PHEONIX said:
These are the schematics that I used to generate the netlist/ratsnet for the PCB layout, so they are exactly the current running topology. As of component values, you may want to do yourself a sanity check, although I'm 99.9% sure everything is fine.
BTW, this is the model for the 2.5V reference:
* Cathode
* Anode | |
* | |
.SUBCKT LM285 A K
Q1 3 2 1 0 NPN1 2.70
Q2 2 2 A 0 NPN1 1
R1 1 A 800 TC=0.00035
R2 4 2 2.4k
R3 4 3 7.2k
R4 5 4 3.28k
Q3 6 3 A 0 NPN1 1
R5 7 6 4k
Q4 10 5 7 0 NPN1 1
Q5 K K 5 0 NPN1 1
R6 2 12 1k
Q6 11 12 A 0 NPN1 0.2
Q9 K 11 13 0 NPN1 2
Q10 K 14 A 0 NPN1 10
R10 14 A 10k
R9 13 14 150
R7 K 8 800
Q7 10 10 8 0 PNP1 1
Q8 11 10 9 0 PNP1 1
D2 A K D1
D1 A 11 D3
R8 K 9 800
C1 K 11 20p
C2 6 3 20p
D3 11 K D2
*
*Adjust output voltage with Is
.MODEL NPN1 NPN(Is=0.8e-14 BF=100 VAF=100 TF=0.5e-9 RB=50 IKF=10m KF=1e-16 AF=1 RE=10)
.MODEL PNP1 PNP(Is=1e-14 BF=50 VAF=50 TF=1e-8 IKF=2m KF=1e-16 AF=1)
.MODEL D1 D(Is=1e-13 Rs=10 CJO=20p)
.MODEL D2 D(Is=1e-13 Rs=10 CJO=2p BV=5 IBV=10u)
.MODEL D3 D(Is=1e-13 Rs=10 CJO=2p )
.ENDS
And the macromodel for the 1.2V reference:
*-----------------------------------------------------------------------------
*
* connections: Anode
* | Cathode
* | |
.SUBCKT LM385 A K
*
* TWO-TERMINAL VOLTAGE REFERENCE
*
DFWD A K DF
GREV A K VALUE={LIMIT(20.00E-3*(EXP(V(A,K)/5.682E3)-1),-10M,0)}
RZ A 1 .102
GZ 2 1 VALUE={LIMIT(EXP(V(2,1)/198.0E-6),0,20.00E-3)}
EBV K 2 3 0 1
RBV 3 0 1.237E3 TC=1.139E-6 -346.8E-9
IBV 0 3 DC 1M
*
.MODEL DF D(IS=39.12E-15 RS=12.18 IKF=0 N=.9983 XTI=3)
.ENDS
Hello Syn08
I understand the point about the bandgap references but the point that I am making is about the the way all the electrolytics (eg C210) are connected to the same ground that the input resistor ( R213) is connectd to. These grounds need to be seperate, and returned to the star point seperatley otherwise you have earthloops and this impacts on distortion and a buzz at the speaker.
Am I missing something.
Regards
AR
I understand the point about the bandgap references but the point that I am making is about the the way all the electrolytics (eg C210) are connected to the same ground that the input resistor ( R213) is connectd to. These grounds need to be seperate, and returned to the star point seperatley otherwise you have earthloops and this impacts on distortion and a buzz at the speaker.
Am I missing something.
Regards
AR
PHEONIX said:
The PCB is using a ground plane. The impedance is very low, so risks of developing a ground loop are minimal.
OTOH this was intended from the very beginning as a dual mono construction.
PGP was using separate grounds, isolated by a small value resistor, but it was experimentally confirmed that this was an overkill. Setting the resistor to zero didn't change anything a iota.
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