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autir
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Posts posted by autir
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Opamps can't drive 4 ohms, a power amplifier is needed.
Can you propose a power amplifier IC family? (1- and 2- input).
Also, can you please explain how can we calculate the value of the voltage-dividing resistors in your sketch?
And why all these capacitors between V+, V- and GND? -
No.
I've come across some circuits which claim to recharge alcaline batteries to a very small degree and for a very limited amount of times. But we don't want acid splashed all over our face, do we? ;D
Just take the batteries to a battery recycling bin and dump them. -
I used to use BC547B and C and BC557B and C transistors when I worked for Philips, but they are hard to get in Canada.
They cost 0.05 Euros each down here.
Want me to send you a hundred or two? ;D -
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Yes, that is why opamps use so many transistors. Class-A transistor stages produce even-harmonics distortion like I showed before with a voltage input.
For the second time you shock me completely.
What about all these people who scorn at op.amps and ICs and design these very expensive class-A amps claiming to be Hi-Fi?
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Dear audioguru
The fact that English is not my native language gives me the right to ask for clarifications regarding your previous answer ;D
What I understand is that I should go for as much high input impedance and as much low output impedance as I can? Like in the ideal operational/differential amplifier model, where Zin=infinite, Zout=0? -
I think the 2SA1015 curves are a fake!
I found the section describing the transistor curves in my theory book.
Yes they are fake. Without any doubt. >:(Then look what happens to the distortion of any transistor with a pure voltage input and the transistor circuit doesn't use any negative feedback:
What I understand from your reply is that it is impossible to replicate with 100% accuracy the input signal? Even with class A?!?
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Hold on a second people!
As we know, the flock of characteristic curves in the Vce - Ic level signify the relation between the incoming (Ib) and the outgoing (Ic) signal. In order for the output signal to be an exact replica of the input (though amplified), the curves must be as parallel as possible.
I attach two pictures. The first is the flock of the BC548, and the second of 2SA1015 from UTC.
As we can clearly see, the cheapo SA1015 I have scavenged from an old radio outperforms the famous BC548. In fact, it makes the perfect amplifier.
I know that this seems too good to be true. Especially the fact that the A1015's curves are COMPLETELY parallel to the x axis. I believe that this is mathematically impossible, but I am not certain.
Your thoughts?
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I am trying to design a class-A audio preamplifier. The very classic design we all know, with 1 transistor, 4 resistors and 3 capacitors.
Should the ideal input impedance be of equal value to the output impedance of the previous stage (e.g. electret microphone)?
Should the ideal output impedance be of equal value to the input impedance of the next stage (e.g. power amplifier)?
Or should the ideal Zin=infinite and Zout=0? -
You could go for a primary switched PSU, no heavy transformer, small size, high efficiency, very small heatsink and heat loss!
Yes, that's what I want :D
Have you got any tutorials/ docs in mind? What should I read to know how to start?
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i get some electronic board from say radio or any other not used device and get all the transistors from it then get their datasheets and put them in boxes for future use. this makes me familiar with many of these transistors.
Exactly what I used to do.
But if I design a circuit and put it on the Internet, I cannot recommend a possibly cheapo, hard to find transistor type.
So, audioguru, I take it as you recommend me to stick just with the BC546-550 family?
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If you take a look at the datasheet, the adjustable output voltage version is what I have in mind. There is no ferrite core transformer in this circuit (or in any other circuits in this datasheet, if I'm not mistaken).
Another problem:
How could I provide the unregulated DC input voltage without use of any heavy power transformer? -
So, as a rule, I buy Op.Amp ICs? And I decide whether I will use these ICs as Op.Amps or create with them a diff.amp. circuit?
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Hi all
I have been searching for electronics' e-shops situated in the European Union for some time - but haven't found anything. By the term "EU" I am referring to the no-toll-tax zone of countries (I am uncertain whether GB is part of the show). Does anyone have something to suggest?
Thanks a lot. -
What are the differences between an operational and a differential amplifier?
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Hello ppl
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Hello all :)
I have decided that the new project I want to build ( a 1.2-30V, 3Amp variable PSU) should have a switching regulator IC instead of a linear one.
After a search I have decided that National's LM2576T-ADJ is an IC well-suited for my needs.
Does anyone have to propose a different solution? It must be in a package suitable for stripboard (TO-220 etc.), and a decent price (<5 Euros) would be a plus.
Thank you. -
http://www.commlinx.com.au/schematics.htm
Look at the "RF" section.
Especially this looks promising. -
Darn... :(
So, since I cannot create PCBs by myself, the only way to build such a circuit is hard-wire?
The PSU I have built (remember that 500mA project?) is soldered on a stripboard and I have not whitnessed any problems... :( -
If you don't use a "star" separate-ground-wires wiring technique, its excellent voltage regulation and ripple rejection are ruined, due to the voltage drop across a common ground wire at high output current.
What exactly is this "star" topology?
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Hi
I use a stereo jack to rca cable
and then I connect the signal to the rca's signal (pin) and ground to the rca's ground (the round metal rim).
It is the simplest, cheapest and most crude way to use an audio card oscilloscope. The fidelity of the signal will be mediocre due to losses caused by the connections and the cables. Not to mention that if you apply excessive voltage you may destroy your sound card (or more...).
The proper way is to build a circuit like this. -
Nice piece! :o
Sixteen general purpose digital I/O lines
That pretty much simplifies things...
All you need then (in the car side of the project) will be the RF transmitter/receiver which will handle digital pulses. Or so I believe?
p.s.: You will still have to install a microcontroller in your house in order to convert data from the lights to digital signal and vice versa.
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The link is dead ::)
Choice of op.amp. model
in Electronics chit chat
Posted
Just downloaded the TL071, TL072 and TL074 datasheets from ST.
In TL071's datasheet the pinout diagram shows the existence of the two offset null pins. There is also the scematic displaying the proper calibration.
In TL074 there are no such pins.
In TL072's datasheet the output from the second opamp is correctly designated as "Output 2", while the output from the first is designated as "Offset null 1".