Page 112 - The Art and Science of Analog Circuit Design
P. 112
William H. Gross
Figure 8-9.
Voltage feedback
from opposite supplies to match, I decided to run a transient response to
fader.
determine how much input degeneration was required.
The bottom fell out! When the fader is set for 10% output, the differ-
ential input voltage is 90% of the input signal! This means that the open
loop linearity of the input stage must be very good for signals up to one
volt or more. To get signal linearity of 0.1% would require over a volt of
degeneration. With that much degeneration in each input stage, the mis-
match in offset voltage between the two would be tens of millivolts and
that would show up as control feedthrough. Big degeneration resistors
Figure 8-10.
Voltage feedback
with cascode
steering.
OUT
