Use hexadecimal data to select a programmable amplifier with a gain of 0 to 15 times

The working principle is very simple. The amplification factor of the inverting amplifier
depends on the ratio of the resistance values
. So the feedback resistor R is set to 80kQ, which is marked intuitively. Use other resistors. The value doesn't matter. To make the amplification
factor 1, take U=80ki:, the amplification factor is 2, R*=40kQ, the amplification
factor is 3, the resistor value should be 26.666kQ, this resistor is virtual - in fact ,
after the data bits (A, port) amplified by l times and amplified by 2 times are connected at the same time, the parallel
resistance value is 80 x 40+(12 0)=26. 666.
    Like this, put the /', 1/^ weighted resistors are connected in parallel in sequence , and
a total resistance of 0-15 times can be obtained.
    In order to control with logic levels, a 4-contact C-MOSlk
pseudo switch can be used. But pay attention to the on-state resistance existence. As for the measures to reduce the error,
some use the same switch and the feedback resistor R, connected in series to become the on state.
However, since up to 4A1 can be turned on, a balance cannot be achieved.
The resistance value should be larger than the transition resistor. To reduce the error (×8 data bits D, its resistance is
.lc}kQ,. If t... is 50QI,, the error is 0.5").