How to make....more accurate voltage follower

225

02:11:28

Is there a way to use feedback in a transistor voltage follower circuit so that it would come as close as possible to perfectly matching the input voltage? Pairing an NPN with a PNP comes pretty close (with the exception of the huge peak low and high differences caused by the biasing of the transistors), but, I'm sure the results could get even better than that, ideally the orange line should stay flat at zero volts the whole time.  I was thinking somewhere along the lines of maybe another transistor that would saturate high if there's a voltage difference between the output of the voltage buffer and the input voltage being buffered and further turn on or off the original transistor, depending upon whether the difference is positive or negative with respect to the input voltage. BUT....   I WANT TO DO IT THE HARD WAY; (NO OP AMPS OR MOSFET'S), because I'd rather learn how the op amps and other ic's achieve such accurate results.  Any help is never taken for granted and is always appreciated :)

Thanks.

published 7 years ago

vytas123

7 years ago

Look into differential pairs and their use in amplifiers. Your voltage follower is in effect an amplification with a gain of 1

Issacsutt

7 years ago

I've seen those, but I would need to convert the two outputs into just one.... do you know of a good way to do that?

jason9

7 years ago

You could just ignore one output. OP-amps use differential pairs and they take the signal from one output of the differential pair and ignore the other.

hurz

7 years ago

What you all know about OpAmps

Issacsutt

7 years ago

The load is supposed to be placed across the two outputs though, I think I would need something that could produce a single output which would go high if theres a significant difference between the two outputs

Issacsutt

7 years ago

...to be discontinued

hurz

7 years ago

The hard way ends as usual for soft issac

hurz

7 years ago

What you call hard way might look like this. You can increase the no of transistors a come closer and closer. You have to make at some point a compromise between precision and complexity. Its totaly unclear what precision you are looking for and if you even know how to define it for problem. But here we go with a three transistor solution which is somewere in the middle of all. http://everycircuit.com/circuit/5576098376318976 dont tell me you dont like the color of the 3rd transistor. Next better solution is with 5 transistors and is almost perfect. Were the final perfect one with about 10 is at the end not perfect, cuz its probably the slowest and most noisy one. The more components are involved the more noise and the slower it will get.

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