Hello
I have a low frequency signal with 10Vpp Amplitude(I can change the amplitude) but the signal is differential.
I have found some 100W or more power amplifier that use MOSFET at the output stage but all of them have single ended input. for example:
DIY 100 Watt MOSFET Amplifier Circuit | Homemade Circuit Projects
or
https://www.diyaudio.com/forums/the-lounge/200865-sound-quality-vs-measurements-1733.html
as you see the input must be single-ended. I need such circuit but with differential inputs. I really need your help.
Best Regards
I have a low frequency signal with 10Vpp Amplitude(I can change the amplitude) but the signal is differential.
I have found some 100W or more power amplifier that use MOSFET at the output stage but all of them have single ended input. for example:
DIY 100 Watt MOSFET Amplifier Circuit | Homemade Circuit Projects
or
https://www.diyaudio.com/forums/the-lounge/200865-sound-quality-vs-measurements-1733.html
as you see the input must be single-ended. I need such circuit but with differential inputs. I really need your help.
Best Regards
can I modify the circuits to apply a differential signal to the inputs? as you see the first stage of the circuits translate a single ended signal to differential so when my signal is differential I think it's better to modify the first stage of the circuits. Thanks
That will not work. Use this stage before the amplifier.
amplifier - Differential to single ended circuit - Electrical Engineering Stack Exchange
Or a balanced, bridged amplifier.
https://sound-au.com/p20_fig3.gif
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I'm no expert, but it seems You are confusing Long Tail pair with differential.
The transistor on the right is connected to the output, so part of the feedback network.
Use an op-amp to convert.
Bear in mind if You use an op-amp before the amp stage You have to attenuate the source signal since it will be double the amplitude after conversion.
1V + -1V inverted = 2V.
PA amps like the Peavey CS800s I own have a differential input from the XLR connector. Made to run from 100' twisted pair cable from the mixer out in the audience. Amp sits on stage to shorten run of large gage speaker cables.
Input op amp is a njm4560 which is pretty quiet & capable.
Input op amp is a njm4560 which is pretty quiet & capable.
It absolutely is possible to use a power amplifier as a balanced to single ended converter.
However, this means that the amplifier feedback node will have to be able to handle the entire common-mode input voltage range. So no ordinary polar electrolytic in the ground leg.
You also get another problem - if you want a decently high input impedance, the power amp inputs are now surrounded by rather high impedances, and those generally are running a decent amount of current and aren't optimized for low current noise. Nothing that some buffer action couldn't fix, but still.
At 10 Vpp in and 100 W / 8 R out, you're also looking at an effective gain of less than 20 dB... might not be trivial to get stable.
I'd suggest handling things the way PA amplifiers do - use a balanced receiver of appropriate (negative) gain, follow it up with a 5k-20k level pot depending on levels, and then go with a conventional power amp of typical gain. (The pros usually shoot for a maximum input sensitivity of 0.775 V and end up with sort of high gains, but I'd see whether you can get along with a typical 29 dB.)
Oh, and if the input cable comes with a shield, connect that to chassis ground. More advanced trickery may be needed if your source impedance isn't low (as in <1 kOhm) and extended bandwidth is required.
However, this means that the amplifier feedback node will have to be able to handle the entire common-mode input voltage range. So no ordinary polar electrolytic in the ground leg.
You also get another problem - if you want a decently high input impedance, the power amp inputs are now surrounded by rather high impedances, and those generally are running a decent amount of current and aren't optimized for low current noise. Nothing that some buffer action couldn't fix, but still.
At 10 Vpp in and 100 W / 8 R out, you're also looking at an effective gain of less than 20 dB... might not be trivial to get stable.
I'd suggest handling things the way PA amplifiers do - use a balanced receiver of appropriate (negative) gain, follow it up with a 5k-20k level pot depending on levels, and then go with a conventional power amp of typical gain. (The pros usually shoot for a maximum input sensitivity of 0.775 V and end up with sort of high gains, but I'd see whether you can get along with a typical 29 dB.)
Oh, and if the input cable comes with a shield, connect that to chassis ground. More advanced trickery may be needed if your source impedance isn't low (as in <1 kOhm) and extended bandwidth is required.
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Start by telling us about that differential signal.
Where does it come from?
Details?
Can it drive lowish impedances, say 1k?
Why did you choose those specific amplifiers?
They CAN be built, sort of, but use obsolete/unavailable components, VERY expensive if found (and then they are often Fakes), maybe those are the first schematics you found when searching?
What is your specific need, what do they have to drive?
Those amplifiers and similar architecture ones CAN be modded for differential input BUT in general input impedance will be low, in the order of 1k .
A better solution, as suggested above, is to add a circuit which turnsa single signal intoa differential one.
Its standard use is to drive 2 amplifiers in bridged mode but it can also achieve what you are asking for, but we need more details.
Please update your Country/Location data, suggestions often depend on that.
Actually I have a sine wave generator, the output of the oscillator circuit has a center tap transformer, the center tap is placed in the primary side, so I have a difference signal from the inputs at the secondary side:
if I want to place the ground at the secondary side, all the even harmonics will be removed and I will have a clean single ended signal. plus as you see I can adjust the signal with changing the inductance of the primary and secondary sides.
I want to apply the signal to the power amplifier.
but if I don't connect the ground to the secondary side I have a differential signal and I think I should modify the power amplifier.
finally I don't want to connect the output of the power amplifier to a speaker, I want to connect the output to a transformer, it could be 200uH to some mH. Actually I want to generate a high power signal.
Thanks
if I want to place the ground at the secondary side, all the even harmonics will be removed and I will have a clean single ended signal. plus as you see I can adjust the signal with changing the inductance of the primary and secondary sides.
I want to apply the signal to the power amplifier.
but if I don't connect the ground to the secondary side I have a differential signal and I think I should modify the power amplifier.
finally I don't want to connect the output of the power amplifier to a speaker, I want to connect the output to a transformer, it could be 200uH to some mH. Actually I want to generate a high power signal.
Thanks
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No. You have a single ended isolated transformer output. Two wires.
In order to have a differential signal (Two complementary signals) You need three wires. One for a phased signal, one for the inverted signal and the other for common of the other two.
You want an amplifier with differential outputs?
We are confused now...
Use an ordinary non BTL amp and run one of the channels inverted.
I see a transformer with an isolated (floating) secondary winding. You can connect this secondary to any amplifier input without generating additional THD.
OTOH, the topic arises the question whether a common power amplifier design that basically resembles a power opamp can play the role of the 3rd opamp in an instrumentational amplifier?
Best regards!
OTOH, the topic arises the question whether a common power amplifier design that basically resembles a power opamp can play the role of the 3rd opamp in an instrumentational amplifier?
Best regards!
howdy,
a signal cannot be categorized as differential or nondifferential. The amplifier (topology) processing it can be differential or nondifferential.
a signal cannot be categorized as differential or nondifferential. The amplifier (topology) processing it can be differential or nondifferential.
Agreed.
I don't see why not, as long as you're keeping an eye on common-mode voltage and minimum stable gain.