Sorry for bothering you guys again! I got the amp working perfectly and know I am just studying it, I figured out star ground and keeping grounding wires short and low as possible, I am wondering why aren't I getting a higher power rating?
Specs:
VCC = 30V
Single Power Supply
Gain = 11
I am getting like 2-3W, where as I should be getting around 14W.
I checked my voltage on the V+ and V-, its both 15V. I checked my resistor gains its 11.
The only thing I can think about and I am not sure if its true, is the heat sinking. Can the on chip internal thermal control stop me from achieving higher power?
Specs:
VCC = 30V
Single Power Supply
Gain = 11
I am getting like 2-3W, where as I should be getting around 14W.
I checked my voltage on the V+ and V-, its both 15V. I checked my resistor gains its 11.
The only thing I can think about and I am not sure if its true, is the heat sinking. Can the on chip internal thermal control stop me from achieving higher power?
Using a dummy load and inputting a 1kHz sine wave Via iphone and measuring the Voltage RMS on my multi meter.
I am using this heat sink but it barely fits on my breadboard due to the dimensions HSE-B254-04H CUI Inc. | Fans, Thermal Management | DigiKey
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Hmm? Its a single supply unit so my V+(NOT VCC) and V-(NOT VEE) is biased at 15V?. DC volts at he output is 0 as it should be and the AC V is 4V RMS. I mentioned I am using a heatsink.
Do you get the same result with 50 Hz or 60 Hz? Rumour has it that some multimeters only work properly with 50 Hz or 60 Hz sine waves.
Hmm I think the multi works at higher frequencies, if you say no ill double check, but my multi meter has a frequency like teller. It can tell you the frequency it sees and it was perfectly outputting 1KHZ output? Do you still want me to check? (Like the meter outputted 1KHZ to verify)
15.96 K/W with natural convection. Add a few K/W for the IC package and the thermal transfer from package to heatsink, and assume that you can allow 100 K of self-heating, and the IC can dissipate about 5 W. As long as you don't play continuous square waves having a peak value of half the supply voltage, that should be OK for a +/- 15 V supply and an 8 ohm load.
Alright just finished testing it, it works with higher frequencies as I got the same Voltage RMS. I got around 6.6V RMS which leads to 5.4 Watts of power.
What chip are you using?
The voltage drops at the output transistors of the chip. And if you use 30 V PSU, a chip gives you +-12 V approximately at its output.
Although 12 Vpk at output is pure 18 watts for 4 Ohm load.
Just try to increase gain level. May be that simple way will solve your problem.
The voltage drops at the output transistors of the chip. And if you use 30 V PSU, a chip gives you +-12 V approximately at its output.
Although 12 Vpk at output is pure 18 watts for 4 Ohm load.
Just try to increase gain level. May be that simple way will solve your problem.
What chip is it? I think most chip amp don't get rail-to-rail output.
Does it really hot that your finger barely able to touch it for 10 sec'?
Gain at 11 on a breadboard likely be your amp will oscillate easily.
Oscillations might explain it; oscillating amplifiers usually suffer from excessive distortion and/or weird hum problems, but there is no guarantee that they always do.
Did you place supply decoupling capacitors very close to the chip and is there a Boucherot network if the datasheet or application note specifies that the chip needs one? Is the output biased at a stable voltage close to 0 V or does the bias voltage change mysteriously when you touch wires? (Touching wires should be quite safe at +/- 15 V.)
Did you place supply decoupling capacitors very close to the chip and is there a Boucherot network if the datasheet or application note specifies that the chip needs one? Is the output biased at a stable voltage close to 0 V or does the bias voltage change mysteriously when you touch wires? (Touching wires should be quite safe at +/- 15 V.)
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I figured it out. It all has to do with the topology I am using, which is the single power supply configuration.
The configuration works by setting the bias of V+ = 15V so its referenced. so essentially you have the "rails" 0 - 15 - 30, where this is 15V difference simillar to a Split supply of +/-15V.
What I didn't notice is that once you AC couple the output it works in similar fashion as a split power supply becoming -15 0 +15. So my rails, is clipping near this where I said 14.981 but due to chip loses around 1V it clips around 13V at the rails
so it makes sense. TLDR;, my rails are at 15V, I was thinking a +/- 30V supply.
The LM1875.
Yea you're exactly right. I was thinking about it wrong. I thought it was 30V to the rails but in actuality is 15V - Vod, oops.
and to answer the rest, its not oscillating. I checked the output at the scope is clean.
Thank you guys for your input! Single power supply configuration is confusing ahah
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