The DA163 quad operational amplifier is the heart of the Hitachi 240 analog computer. This is the only active component of the analog part of the machine. Each DA163 module contains four identical, chopper stabilized operational amplifiers.

Due to the chopper stabilization these amplifiers exhibit only a very low drift due to temperature changes, etc. In contrast to the operation amplifiers used in the RAT700 analog computer build by TELEFUNKEN in 1959 the DA163 uses a fully electronic chopper (with a special switching transistor as its heart) while the TELEFUNKEN machine, built ten years before the HITACHI 240 uses an electromechanical chopper relays.

In the middle of the picture on the right the electronic chopper can be seen. Each of the two printed circuit boards mounted on top of each other contains the necessary electronics for two chopper stabilized operational amplifiers. The symmetric construction is quite visible in the picture.

Behind the patch panel