Hi everyone,
I saw a sub amp using an LM3875 with TIP35C/TIP36C as outputs. Has anyone tried this? Can you please point me to a schematic?
Thanks in advance,
Best Regards,
JojoD
I saw a sub amp using an LM3875 with TIP35C/TIP36C as outputs. Has anyone tried this? Can you please point me to a schematic?
Thanks in advance,
Best Regards,
JojoD
paulb,
I have searched but can't find anything about it in here.
If there is anyone who remembers it please point me in the right direction.
Thanks,
JojoD
I have searched but can't find anything about it in here.
If there is anyone who remembers it please point me in the right direction.
Thanks,
JojoD
Look for the datasheet from UTC for the TDA2030
http://www.unisonic.com.tw/spec/UTC TDA2030A.pdf
You will see a circuit, maybe the same you see with 3875
http://www.unisonic.com.tw/spec/UTC TDA2030A.pdf
You will see a circuit, maybe the same you see with 3875
Hi Kay,
I built that just now. However, the chipamp is warm but the transistors are not even warm. I used MJ15003/4 pair for the output. If you have any other ideas on such a project, please inform me.
Thanks,
JojoD
I built that just now. However, the chipamp is warm but the transistors are not even warm. I used MJ15003/4 pair for the output. If you have any other ideas on such a project, please inform me.
Thanks,
JojoD
http://www.mif.pg.gda.pl/homepages/tom/files/simp200W.gif
This circuit with an 80V supply and the National Semiconductor LM3886/whatever, will drive 400W/4R with MJ15003/04. If you want to use plastic TIP35/36 use twice as many.
This circuit with an 80V supply and the National Semiconductor LM3886/whatever, will drive 400W/4R with MJ15003/04. If you want to use plastic TIP35/36 use twice as many.
this is pretty interesting...haven used a GC chip this way...I'll try it out soon and let you guys know hat I used and what's the performance like...but has anyone actually done it???
Can we use that circuit with one LM1876 and two MJ3055+MJ2955? And does it give 200W RMS to 4ohm?
And the final question; does the SOAR work in this situation?
And the final question; does the SOAR work in this situation?
And the finalest question;
Whats that circuits gain? I cannot read it from schematic. On the (-) pin there are many resistors. 100K, 3K3, another 3K3 does makes 100K/6K6 so 15,15+1= 16,15... Is it true?
Whats that circuits gain? I cannot read it from schematic. On the (-) pin there are many resistors. 100K, 3K3, another 3K3 does makes 100K/6K6 so 15,15+1= 16,15... Is it true?
uhhh....what's SOAR?? Izzit SpiKe?? I think the 2955 wun be able to handle the volatges...(SOA) get a better alternative....
And the most finalest and the stupidest quesiton ever;
- Can we use the left (or right) part of that circuit to drive a 2ohm load and can we have 100W?
- Is there life out of the world, whats the lifes meaning, does the life after life exists.....
- HOW CAN WE USE THAT SIMILIES IN THE TEXT?
- Can we use the left (or right) part of that circuit to drive a 2ohm load and can we have 100W?
- Is there life out of the world, whats the lifes meaning, does the life after life exists.....
- HOW CAN WE USE THAT SIMILIES IN THE TEXT?
Yes I guess SOAR is the sPike, thermal protection, short circuit protection etc.. And what transistors u recommend? (European pls..)
Thanks..
Thanks..
JojoD818 said:
You must adapt the resistors between +/-VCC and the base of the Transistors, to get a correct idle.
Compare Tietze/Schenk: Schaltungstechnik
If I remember correct, you need about 400mV between Base and Emitter.
Dxvideo said:
You need only one part. This circuit shows the bridged version.
So you mean; I will put a LM1875+2n3055/2955 and I get 100W to 2ohm load? Does it work? Ligangyi says 2955 cannot handle that voltage! Which transistor pairs I must use?
Thanks
Thanks
a 3055 running at +-40V and above is skirting near it's line and is super risk..you cpould try it just for kicks...but you might end up with blown parts...go get something that will at least handle 150V...
Dxvideo,
To cut it short, you can use MJ15003/4 or MJ15024/25 pairs.
Guys,
What I did was the one included in the 2030 datasheet but I used a dual supply (+/-), anyway it seems that the power transistors were not conducting since they are not even getting warm (ops on a separate heatsink). But I used a 1.2 ohm resistor but in the new diagram (from djk), it is a 2.2 ohm resistor. I tried a 5 ohm resistor for a short while and I can feel the transistor's heatsink becoming warm.
BTW, you may ask, why do you want to heat up the output transistors? No, I don't want them to get hot, I just want to make sure that they are helping the chipamp in delivering much needed power output.
Questions:
1. Voltage drop accross the resistor on the supplies is equal to the Base-Emitter voltage, so is there a simple formula for this? The reason is assuming that this topology will be used for different chipamps that has different supply voltage.
2. What is the "optimal" Base-Emitter voltage for the output transistor to make sure that they are conducting?
Best regards.
JojoD
To cut it short, you can use MJ15003/4 or MJ15024/25 pairs.
Guys,
What I did was the one included in the 2030 datasheet but I used a dual supply (+/-), anyway it seems that the power transistors were not conducting since they are not even getting warm (ops on a separate heatsink). But I used a 1.2 ohm resistor but in the new diagram (from djk), it is a 2.2 ohm resistor. I tried a 5 ohm resistor for a short while and I can feel the transistor's heatsink becoming warm.
BTW, you may ask, why do you want to heat up the output transistors? No, I don't want them to get hot, I just want to make sure that they are helping the chipamp in delivering much needed power output.
Questions:
1. Voltage drop accross the resistor on the supplies is equal to the Base-Emitter voltage, so is there a simple formula for this? The reason is assuming that this topology will be used for different chipamps that has different supply voltage.
2. What is the "optimal" Base-Emitter voltage for the output transistor to make sure that they are conducting?
Best regards.
JojoD
>2. What is the "optimal" Base-Emitter voltage for the output transistor to make sure that they are conducting
you had to find a correct idle current, so measure the distortions
you had to find a correct idle current, so measure the distortions
"i assume you mean you mean +/-40."
Actually, no.
If you look at the diagram it is a single xxV supply. The only ground current you need is the input off-set current for the diff input in the IC, that is what the 100K resistor on the input is for. The pair of 2K2 at the right side provides the ground reference for the input.
Observe the maximum voltage ratings for the parts, an LM3875/76/86 is 84V absolute maximum, I would use no more than 80V on it. An LM1875 is 60V absolute maximum, I would go no more than 95% of this, or 57V
3055/2955 are 60V parts, get the 'C' version of the TIPs for the 100V parts.
"Can we use that circuit with one LM1876 and two MJ3055+MJ2955? And does it give 200W RMS to 4ohm?"
Look at the circuit. The booster transistors are driven from the IC power supply pins. Stereo ICs do not have stereo power supply pins. You have to use mono ICs.
While two LM1875 and two each 3055/2955 on 57V will do 200W/4R, it is pushing it hard. The gain on the 3055/2955 at 10A is quite poor, it will work though, the LM1875 will have to drive a couple of amps base current into the boosters.
"And the final question; does the SOAR work in this situation?"
After a fashion. The booster transistors should have emitter resistors, between 0R1~0R33 are about right. The BE resistors (2R2 shown in schematic) set the ratio of current flowing through the IC vs the booster transistors. For any current limiting to occur this resistor must be selected so that as the Beta on the booster transistors drops near maximum output, and that more current is drawn from the IC direct. The resistor values will be more like 0R68 rather than the 2R2 shown. The IC must track the temperature of the outputs (mount to the same sink).
On a short circuit, the Beta will drop on the boosters and the IC will have to make up the current. The IC will then go into protection. If you overheat the boosters it will heat up the IC and go into SPIKE protection. Since the TO3 transistors have a higher maximum junction temperature than the plastic IC, this works better than you think.
"Whats that circuits gain? I cannot read it from schematic. On the (-) pin there are many resistors. 100K, 3K3, another 3K3 does makes 100K/6K6 so 15,15+1= 16,15... Is it true?"
The second 3K3 has a 1N5 in series with it to reduce gain at high frequencies (above 32Khz), the 10µF forms a pole at 4.8hz with the 3K3. Gain is about 36dB, change the right hand 100K to 103K3 for best balance (no real need).
"Can we use the left (or right) part of that circuit to drive a 2ohm load and can we have 100W?"
Sure, just remember to use ± supplies since you are no longer bridged.
"You must adapt the resistors between +/-VCC and the base of the Transistors, to get a correct idle.
Compare Tietze/Schenk: Schaltungstechnik
If I remember correct, you need about 400mV between Base and Emitter."
Do not try and force an idle current through the boosters. Tweak the BE resistors for correct protection action at full power. I would want no more than 340mV BE on the boosters at idle. 340mV is the same amount of bias used in the output stage of a Crown DC300A and the Phase Linear 400.
Actually, no.
If you look at the diagram it is a single xxV supply. The only ground current you need is the input off-set current for the diff input in the IC, that is what the 100K resistor on the input is for. The pair of 2K2 at the right side provides the ground reference for the input.
Observe the maximum voltage ratings for the parts, an LM3875/76/86 is 84V absolute maximum, I would use no more than 80V on it. An LM1875 is 60V absolute maximum, I would go no more than 95% of this, or 57V
3055/2955 are 60V parts, get the 'C' version of the TIPs for the 100V parts.
"Can we use that circuit with one LM1876 and two MJ3055+MJ2955? And does it give 200W RMS to 4ohm?"
Look at the circuit. The booster transistors are driven from the IC power supply pins. Stereo ICs do not have stereo power supply pins. You have to use mono ICs.
While two LM1875 and two each 3055/2955 on 57V will do 200W/4R, it is pushing it hard. The gain on the 3055/2955 at 10A is quite poor, it will work though, the LM1875 will have to drive a couple of amps base current into the boosters.
"And the final question; does the SOAR work in this situation?"
After a fashion. The booster transistors should have emitter resistors, between 0R1~0R33 are about right. The BE resistors (2R2 shown in schematic) set the ratio of current flowing through the IC vs the booster transistors. For any current limiting to occur this resistor must be selected so that as the Beta on the booster transistors drops near maximum output, and that more current is drawn from the IC direct. The resistor values will be more like 0R68 rather than the 2R2 shown. The IC must track the temperature of the outputs (mount to the same sink).
On a short circuit, the Beta will drop on the boosters and the IC will have to make up the current. The IC will then go into protection. If you overheat the boosters it will heat up the IC and go into SPIKE protection. Since the TO3 transistors have a higher maximum junction temperature than the plastic IC, this works better than you think.
"Whats that circuits gain? I cannot read it from schematic. On the (-) pin there are many resistors. 100K, 3K3, another 3K3 does makes 100K/6K6 so 15,15+1= 16,15... Is it true?"
The second 3K3 has a 1N5 in series with it to reduce gain at high frequencies (above 32Khz), the 10µF forms a pole at 4.8hz with the 3K3. Gain is about 36dB, change the right hand 100K to 103K3 for best balance (no real need).
"Can we use the left (or right) part of that circuit to drive a 2ohm load and can we have 100W?"
Sure, just remember to use ± supplies since you are no longer bridged.
"You must adapt the resistors between +/-VCC and the base of the Transistors, to get a correct idle.
Compare Tietze/Schenk: Schaltungstechnik
If I remember correct, you need about 400mV between Base and Emitter."
Do not try and force an idle current through the boosters. Tweak the BE resistors for correct protection action at full power. I would want no more than 340mV BE on the boosters at idle. 340mV is the same amount of bias used in the output stage of a Crown DC300A and the Phase Linear 400.
- Status
- Not open for further replies.