Hey Peeps
Please forgive me if I make any mistakes here as I am a newb.
Wondering if someone could please help me though -
I'm building a guitar amp from scratch from discrete components, trying to opt away from op-amps (excuse the pun hehe) and do it the good old fashioned way to learn as much as possible along the way and to say that "look mum I did this all by myself with no hands" ..well with hands but..you know what I mean.
I've got my voltage gain sorted out.
I worked out that my pickup produces 100mv of voltage and if I want clean undistorted sound up to the rails on my +/- 37 volt power supply and so I need an amplifier with a voltage gain of 370. Is that correct?
Now I just need the current gain ...I have no idea what kind of power my pickups are producing and have no way of measuring it, I have a multimeter with a.c voltage reading but no oscilloscope or anything. I could possibly put a resistor across the pickup and measure voltage drop but..nah, silly idea...I'm begging someone will please just give me the answer.
So I have a push pull stage in darlington pair configuration for my power side of the amp (which I have built on a breadboard) and have calculated the total current gain to be 200 (for one side NPN or PNP) ...does that mean that it has actually current gain of 400? I got the 200 by multiplying the HFE of the first NPN transistor by the HFE of the second transistor.
And I can work backwards from there and work out the current gain of each stage but that doesn't really help as I need to know what I need to amplify in order to be able to build the stages for it.
Also wondering - for power calculation purposes...
Hypothetically if I have a class a common emitter stage with a transistor with a HFE of say 50 and I run 50 volts as the power supply....
will the current gain remain at 50 or does this HFE value only apply if the transistor is run in common collector mode? (as a current amplifier not a voltage amplifier) ?
I am also wondering....is the current output of the small signal important... IE -
If I run an op amp that produces 32ma but a voltage of +/- 37 does that mean that to calculate my power I use ohms law to calculate Volts X amp's = W? (Bearing in mind the root mean squared thing with amps, can't remember what it's called but that 1.4 number that we have to divide by)
I guess my question here is...will the small signal current gain have much effect on the final product (speaker) or is it more about voltage? (as is the case with mosfets being voltage controlled valves as opposed to b.j.t's being current controlled.
Any help appreciated - thanks
Please forgive me if I make any mistakes here as I am a newb.
Wondering if someone could please help me though -
I'm building a guitar amp from scratch from discrete components, trying to opt away from op-amps (excuse the pun hehe) and do it the good old fashioned way to learn as much as possible along the way and to say that "look mum I did this all by myself with no hands" ..well with hands but..you know what I mean.
I've got my voltage gain sorted out.
I worked out that my pickup produces 100mv of voltage and if I want clean undistorted sound up to the rails on my +/- 37 volt power supply and so I need an amplifier with a voltage gain of 370. Is that correct?
Now I just need the current gain ...I have no idea what kind of power my pickups are producing and have no way of measuring it, I have a multimeter with a.c voltage reading but no oscilloscope or anything. I could possibly put a resistor across the pickup and measure voltage drop but..nah, silly idea...I'm begging someone will please just give me the answer.
So I have a push pull stage in darlington pair configuration for my power side of the amp (which I have built on a breadboard) and have calculated the total current gain to be 200 (for one side NPN or PNP) ...does that mean that it has actually current gain of 400? I got the 200 by multiplying the HFE of the first NPN transistor by the HFE of the second transistor.
And I can work backwards from there and work out the current gain of each stage but that doesn't really help as I need to know what I need to amplify in order to be able to build the stages for it.
Also wondering - for power calculation purposes...
Hypothetically if I have a class a common emitter stage with a transistor with a HFE of say 50 and I run 50 volts as the power supply....
will the current gain remain at 50 or does this HFE value only apply if the transistor is run in common collector mode? (as a current amplifier not a voltage amplifier) ?
I am also wondering....is the current output of the small signal important... IE -
If I run an op amp that produces 32ma but a voltage of +/- 37 does that mean that to calculate my power I use ohms law to calculate Volts X amp's = W? (Bearing in mind the root mean squared thing with amps, can't remember what it's called but that 1.4 number that we have to divide by)
I guess my question here is...will the small signal current gain have much effect on the final product (speaker) or is it more about voltage? (as is the case with mosfets being voltage controlled valves as opposed to b.j.t's being current controlled.
Any help appreciated - thanks