Javalab
![]() |
Lars Drud Nielsen ldn@oersted.dtu.dk |
Chose a large value of the opamp gain (typically >100 dB) in order to ensure a reasonable accuracy of the virtual-ground principle.
Notice: With regard to the exercises below the various resistors in the circuit offer different ranges of resistance values.
In all cases: Adjust the feedback resistance (3. column) to achieve a nice scaling of the analogue output, still avoiding saturation of the opamp for any legal input combination!
Simple summation amplifier:
Let all resistances in the 1. column be equal.
Let both resistances in the 2. column be zero.
8-bit D/A converter:
Keep both resistances in the 2. column to zero.
Assign proper values to the resistances in the 1. column.
2-digit BCD D/A converter:
Let the two groups in the 1. column represent the two digits,
MSD = most significant digit,
LSD = least significant digit.
In the 2. column let the MSD resistance be zero
and assign the proper value to the LSD resistance.
(Another choice of this resistance value will make the converter
back to simple 8-bit again!)