Programmable amplifier with gain from 10 to 90dB selectable in 10dB increments

Although the basic circuit of the Zhi amplifier is a non-phase AC amplifier, there are no
special changes. However, in order to select the correct amplification factor, the circuit uses
a resistance value of 9k0. that is not available in the Chou series resistors. OP37 was selected as the input amplifier Ai
  (even if the amplification factor is large, the deterioration of the characteristics is very small, and there is no phase compensation
). In order to remove the broadband noise in the power supply line, the circuit is added with
'', g5 and chu5, Filter composed of c4. Although general OP amplifiers can be used for Ai ~As
, the conversion speed should be above 10 V/"s.
    In order not to increase the DC offset voltage, 1011F capacitors are used in the backup amplifiers
, so that the win-current amplification factor is 10