Electronics > Beginners
Odd Glitch In Waveform
magic:
Post the schematic. You can't make an amplifier with just one MOSFET, even Nelson Pass can't do it :P
Fundamental question about every speaker: what impedance, what power.
codingwithethanol:
@magic
Schematic is same as before except electret mic is input not function generator. Also the feedback resistor is 100k now. Output of the amp varies from under a volt to clipping depending on what the mic is picking up. Speaker is 12ohm 5W, I set my function generator to 1k sine 1V p-p and the tone was low but audible so 5V-10V should be earpiercing.
David Hess:
--- Quote from: magic on February 12, 2020, 07:56:58 am ---Dual 741 was 1458 and 4558 is a slightly different animal.
4558 is what goes into all those NE5532's on auction sites and fetches 100% positive feedback so it's clearly good enough for audio :D
--- End quote ---
The 4558 has "741 type" performance but is otherwise very different. The quad RC4136 is the same way. The basic difference is that they use a PNP differential input stage to get a wide differential input voltage range, like a 324/358, while the 741/301 type of operational amplifier uses a PNP cascaded with the NPN differential stage. The reason this works is that the PNP transistors built on these NPN processes have a high base-emitter breakdown voltage.
The major difference is that the input bias currents are reversed which causes problems in some circuits.
--- Quote from: Cerebus on February 11, 2020, 03:03:45 am ---That trick wouldn't work here, the 741 has a proper class AB totem pole output unlike something like the LM358 where exactly that trick is often called for to compensate for the weaknesses of the lop-sided class B output stage. I also suspect you're thinking about the LM358 when you talk about a proneness to crossover distortion; there's no bias applied to the output transistor bases on the LM358 to offset the VBE drops on the output transistors - it operates in pure class B and relies on external negative feedback to get rid off the problem. The LM741 has a classic VBE multiplier used to bias the output transistor bases into the active region in classic class AB operation.
--- End quote ---
It still works to force class-A operation but that is of more limited use when the output stage is already class-AB.
nigelwright7557:
The very old 741 has all sorts of problems.
Poor bandwidth, not rail to rail,crossover distortion, lower input impedance than JFET device.
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