Transistor amplification 101 – Erica Synths EDU DIY Dual VCA Eurorack Module Kit User Manual
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TRANSISTOR AMPLIFICATION 101
Okay, but if we can’t use transistors as voltage controlled resistors, then how can we use
them? Well, one of their main applications is actually amplification.
Transistors can take
a very small voltage swing and scale it up massively
. One way to do this is by setting
them up in what’s known as the common emitter amplifier configuration. At its most
basic, it could look like this:
Here’s how it works. We apply a very weak little 20 mV peak-to-peak signal with a
comparably big 570 mV o
ff
set to the transistor’s base, while monitoring the voltage at the
transistor’s emitter. And here we’ll notice something strange. Compared to the oscillation
we send into the base, there’s a huge voltage swing at the collector that looks a lot like it,
just slightly distorted. What’s up with that? To answer this, we’ll first have to understand
the way the base voltage relates to the amount of current allowed to flow between our
transistor’s collector and emitter.
You can try this chapter’s circuits in a simulator. I’ve already set them up for you right here:
you can change all values by double clicking on components.
Yup, it’s also inverted. But this is not really important for our purposes here!
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