
48 Analog Circuits Cookbook
but the output at 45 kHz was 3 dB down. Distortion looked distinctly
secondish, whereas the limiting mechanism is clipping in the balanced
second long-tailed pair. This should be a symmetrical phenomenon and so
only produce odd-order distortion products.
The base terminals are internal to the circuit and so inaccessible, but not
so the first LTP. Suspecting offsets in the long tailed pairs, I added a 100k
pot across the +15 V and -15 V supply rails with a 150kQ resistor from the
wiper to pin 15. Adjusting the pot, the distortion was reduced from 0.3%
to 0.2%, being then nearly all third harmonic as expected. Wit