Erica Synths EDU DIY Wavefolder Eurorack Module Kit - Manual (Page 22)

BUFFERED WAVEFOLDER
To get there, let’s first clean up the existing schematic while keeping the circuit itself the
same. We’ll move the two transistors directly on top of each other. Then, we’ll pull both
collector resistors over to the right.
This leaves us with these two vertical paths on and between which current flows. Let’s
take a closer look at the one on the right.
Since this is a 50% voltage divider between +12 V and
-12 V, the central node sits at 0 V. At least until we start
drawing current from it. Then, the voltage will drop by
100 mV for every additional 10
μ A we pull through the
top resistor.
Interestingly, we can get exactly the same behavior
from a single 10k resistor to ground
: if we don’t pull
current through it, the voltage on the other side is 0 V.
And if we do, the voltage drops by 100 mV for every 10
μ A we pull. Great! So we could simply replace the two
20ks with a single 10k to ground and save ourselves a
resistor.
But we can take the optimization even further. We’ll use an inverting bu ff er to bu ff er the
collector voltage – instead of a non-inverting one.
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